Despondency Is An Act of Kufr
Hazrat Hakeem-ul-Ummah (RA) has mentioned that a fistful of gunpowder can cause an entire mountain to crumble into little pieces. So when a small amount of gun powder has the effect to blow up an entire mountain, so then the mercy of Allah also has the effect that when the focus of His mercy is directed towards us and allows us to repent for our sins the size of mountains, then weighty mountains of our sins would just blow up into thin air as if they never existed. Is not the mercy of Allah greater than gunpowder?
Being despondent of the mercy of Allah is an act of kufr. One should never lose hope in Allah. Regardless of how great in quantity or quality our sins may be, at the end of the day they are limited. However, our link is with that being whose mercy is unlimited and infinite. Therefore, we should be grateful that Allah’s mercy is infinite and is able to encompass our finite sins and wipe them out.
So take out some time, offer two rak’ats of Salat-ut-Tawbah, and supplicate to Allah in the following way, “O Allah, ever since I became an adult (baligh) till now, whatever sins I have committed, please forgive all of them.”