This is from Satan. Whenever you do good deeds, he makes you proud of them and gives you the feeling that you have credit and you can afford to sin as this would cover your sins.

That is why, when you do good deeds, you should always be afraid that Allah may not have accepted it. this encourages you to do more good deeds and less bad ones as you don’t know whether Allah will forgive you or not.

Why is it whenever I do a good deed & then straight after that I commit a sin & then I feel as if my good deed won’t get accepted?