So never get bogged down in thinking what you have done is too bad. We are human we make mistakes Sometimes the same mistake over and over again. A few points that Sheikh Hesham made in his talk, I would like to highlight are:
1) Allah's mercy is boundless Allah was willing to forgive firaun, the biggest tyrant the world has ever seen, who murdered new born children and who enslaved a whole nation.(20:44) So if Allah was willing to forgive Firaun we definitely have a chance, if we reflect on this for a second it is so re assuring.
2) Don't Delay in Repentance As soon as you commit a sin immediately remember Allah and ask him to forgive you
3) Don't try and rationalise and justify your sin too many times we add a but after the admission of a sin to ourselves. We should understand when we sin we are in the wrong and it is just one battle we have lost in the war against shaytaan and our nafs. It is not "who we are" it is a temporary situation we have the power to change, with the help of Allah.
4)Take the sin seriously