How do you get over something you done

Serious answers only on this one. Where mental health has been a factor in people's lives and you never really addressed it and that makes you mess up something so bad it can probably never ever be undone how have you got over the impact when you suddenly realise what you have done. Am starting therapy but want to hear it from people that have been through a similar situation personally because right now the primary emotion flooding me is remorse and its so hard to see the future you had expected wrecked because of out of control actions. I wont be giving details of what its not about that its about dealing with that realisation