Refraining From Sins is Genuine Worship

"Abstaining from sins is the basis of religion. Hence, refrain from sins in order to become the most pious worshipper. Adorn yourself with piety. Do not perform a single good deed without piety. Surely that deed is most acceptable by Allah which is accompanied by piety, even though it may be trifle. As Allah says, "Allah accepts the good deeds only from the pious people."
(Iddatud-Dai)

Hence if you succeed in remaining aloof from sins, then even if your good deeds are paltry, they would be accepted by the Lord. And when the Lord of the Worlds accepts a deed it cannot be termed as trifle or paltry.

Avoidance of Sins is a Must:

Considering the tradition quoted above one is compelled to conclude that it is necessary to dread sinful acts and to be ever cautious of the vices. Only then are the good actions of any consequences. The good deeds must also be performed in such a manner that we strive to emulate as closely as possible the examples set by the high ideals of our Ahlul Bayt (a.s.). It should not be that good actions are rendered null and void due to sins. It is necessary to be cautious of such an impending loss and disaster for which we ourselves would be responsible.

Good Actions Could Be Blown Away Like Dust

Sulaiman bin Khalid says; " I asked Imam Ja'far as-Sadiq (a.s.) regarding the Quranic verse

(And We will proceed to what they have done of deeds, so We shall render them as scattered floating dust.
(Surah Furqan 25:23)

He said,
"By Allah, even if their deeds are as white as Egyptian cotton, but if they find sin and lewdness they do not abstain from it."
(Iddatud-Dai)

In other words, their good deeds are scattered like dust due to the lack of piety, and hence are of no value at all. Allama Majlisi (r.a.) writes in the explanation of this tradition, "Worship and obedience is rendered null due to sin."

A Large Number of Pious People Will Enter Paradise

Imam Ja'far as-Sadiq (a.s.) said,
"Allah revealed to Hazrat Musa (a.s.), "Verily, My slave cannot achieve nearness to Me without the three things which I like." Musa (a.s.) asked with reverance, "My Lord what are those three things?" Allah replied, "O! Musa those three things are: To practice piety in this world, to abstain from sins and to weep due to fear." Musa (a.s.) asked, "Does one who fulfills the three things gets compensation and reward?" Allah replied, "One who practices piety in this world will get Paradise. One who weeps due to My fear will be accorded such a high position that no else would be able to reach it. The deeds of all the creatures shall be accounted. But one who abstains from that which I have forbidden, then accounting of his deeds will not be carried out; he would be admitted to Heaven directly." 

Abstaining From the Greater Sins Cause the Lesser Sins to be Overlooked

If one avoids the Greater Sins, the Lesser sins shall be overlooked. Allah, the Almighty, by His grace, excuses the Lesser sins. As it is mentioned in the following verse of the Holy Qur'an
"If you shun the Greater Sins which you are forbidden, We will do away with your smaller sins and cause you to enter an honourable place of entering."
(Surah Nisa 4: 31)

The Gates of Paradise are Open for the Pious

The Holy Prophet (s.a.w.s.) is reported to have said,
"I swear by Allah, in Whose power is my life, there is not a single person who prays five times a day, fasts during the month of Ramadhan and abstains from sins that the gates of Paradise will not be opened for him."
After this he recited the Qur'anic verse quoted above.
(Tafseer Minhaajus Saadeqeen)

Intercession

A person who commits a Greater Sin and does not repent for it, is a transgressor. Namaz is not allowed behind him (he cannot lead a prayer assembly). His testimony is unacceptable. After death, he is liable for Divine punishment. By the Grace of Allah such a person may yet get salvation; and the Grace of Allah that can make this possible is the intercession of Muhammad (s.a.w.s.) and his Progeny (a.s.).

As the Holy Prophet (s.a.w.s.) says in one of his traditions:
"My intercession has been kept for the sinful among my followers."
(Behaarul Anwaar vol.3).

He (s.a.w.s.) also said,
"My intercession is specially for the sinful ones among my followers. But those who abstain from the Greater Sins, for them there is no accounting (of deeds)."

That is, they would be admitted to Paradise right away.

Intercession Should not Prompt one to Commit Sins

There is hardly any doubt regarding the reality of Shafa'at (intercession). Actually it is the right bestowed upon the Holy Prophet (s.a.w.s.) and the purified Imams (a.s.), by Allah, to show their greatness and position. The other aim of intercession is to make their respect evident. The people who have committed Greater Sins shall be entrusted to them. By the grace of their intercession the sinful people will be able to ascend the heights like other groups of people. All this is evident from the Holy Qur'an and the authentic reports. It is also clear from Mutawatir (most frequently related) traditions. It would be needless to relate all such traditions for such a short discussion.

Only one point must be stressed at this stage. Intercession should not be taken as a license for committing sins nor should it make one heedless of repentance.

Suicide in the Hope of Salvation

To sin and not to repent in the hope of intercession is akin to consuming poison or putting ones hand in the snake's mouth with the hope that a doctor would arrive and cure you. It is against logic, because after consuming poison it cannot be taken for granted that medical assistance would be available. Even if a doctor and medicines arrive on time it is still difficult to say that life would be saved. Before the medicine could have any effect the poison may spread to the whole body and death may occur.

In the same way, one who performs lewd actions in the hope that he would be interceded after death; cannot be confident that intercession will come to the rescue immediately.

Death is of Three Types

Imam Muhammad Taqi (a.s.) has related from his forefathers that Amirul Momineen Ali (a.s.) was queried by someone about death. He replied,
"You have come to the knowledgeable (personality)." "Death occurs to a person in one of the three ways:
He is given the good news of everlasting bounties, or informed of the never-ending retribution or he remains in a perpetual state of terror and fear.

His affair lingers undecided and unpredictable, and it is not known about the kind of future that awaits him. Then (you must know) that our devotee who is obedient of our command and does not sin, is given the good news of everlasting bounties. But our opponent shall forever be involved in Divine punishment. And the person who has been unjust to his soul and who has abused it will be found in an unsure condition. Unaware of what the future will hold. Such a person is a sinner whose death will be accompanied with terror and fear. But Allah will not consider him on the same level as our enemy. Rather he would be removed from Hell because of our intercession.

Then, act (rightly) and obey the commandments of Allah. Do not consider the Divine punishment to be trifle, and certainly there are such people who would not be able to receive our intercession till after 3,00,000 years."(Behaarul Anwaar vol.3 quoted from Ma'aniul Akhbaar)

I am Concerned About You Regarding Barzakh

Umar ibne Yazid says that, "I asked Imam Ja'far as-Sadiq (a.s.), "I have heard you saying that all our Shia's will enter Heaven however sinful they may be?" Imam replied,
"By Allah I had truly said, they shall all belong to Heaven."

Then I asked, "May my life be sacrificed upon you, even if their sins are great and in large number?" Imam said,
"All of you (Shias) shall enter Paradise by the intercession of the Holy Prophet (s.a.w.s.) or his successors on the Day of Judgement. But, by Allah I fear for you the Barzakh."

I asked,"What is Barzakh?"

He replied,
"Barzakh is the grave. Its duration commences from the time of death until the Day of Judgement."
(Al Kafi)