After you sin, Shaytan tries to make you do one of two things. The first thing that he will do is try to make you feel like there is no point in even repenting. However if you do repent, he will use his second move and that is making you think your repentance will not be accepted.
Allah tells us in the Quran that we should never lose hope in His mercy, so by doubting that He will forgive you, you are insulting Allah the Most High.
How can we dare to disagree with Allah when He clearly tells us that a sincere repentance will always be forgiven. Don’t ever lose hope. Don’t ever let Shaytan convince you that Allah will not forgive you.