Haafiz Ibn al-Hajar said:
Do not let how evil you think you are and the high number of your sins stop you from making dua to your Lord because He answered the devil (ibliis) when he said: O my Lord, give me respite until the day when they are resurrected.
Allaah said: Indeed, you are from among the ones given respite.
The devil disobeyed Allaah. Allaah cursed him. Ibliis made dua despite all of this, and Allaah answered his dua.
You may think you are very evil. You know you have loads of sins. Do not allow this to stop you from making dua to Allaah because the dua of the devil was answered who is much worse than you.