How shall Allah guide a people who have disbelieved after their faith and [after] bearing witness that the Apostle is true, and [after] manifest proofs had come to them? Allah does not guide the wrongdoing lot.
(Quran Surah Al-Imran 3:86)
When a person really gets down and starts thinking of all the good deeds he or she has done, a good, warm feeling begins to develop within him or her. Having helped someone in need, fed the hungry, put a smile on someone’s face, helped someone in their work or simply having removed and obstacle from the road all count as good deed and Allah (SWT) rewards people for them. The basic purpose of humanity is to worship Allah (SWT) and to do good so that we may procure His favour and find success in the afterlife. However it is quite common especially for the weaker of faith believers to become anxious in thinking if all these seemingly small deeds have any kind of significance in front of Allah (SWT) since they have committed many sins too. Some sins are small and some sins are big. However always remember that no matter how grave the sin, the mercy of Allah (SWT) is infinite and greater. Allah (SWT) says in the Quran,
“O My servants who have transgressed against themselves [by sinning], do not despair of the mercy of Allah. Indeed, Allah forgives all sins. Indeed, it is He who is the Forgiving, the Merciful.”
(Surah Zumar 39:53)
This is the most important factor where good deeds are concerned. Every good deed according to the Islamic doctrine will be rewarded based on the intention. Having a pure intention is the key to finding success in this world and the next. If a good deed is done solely to please Allah (SWT) and obtain His mercy, than that deed will indeed be rewarded.
The main purpose of doing good deeds in this world is to gain the forgiveness from Allah (SWT) and to find success in the afterlife. Every person is going to be judged according to the deeds he or she committed in the world and paradise and hellfire depend on those deeds for a person. However if a person is truly sorry for his evil that he has committed, he should never be depressed or hopeless since as mentioned above, there is no sin in this world that Allah (SWT) does not forgive with begged repentance for.