Yesterday is the day that will never come back, and it never should. Whatever is in the past, let it remain there. The past could be our podium to grow from, but never an anchor that should drag us down.
Learn to release your past and live in the present moment.
I wrote this a few years ago, but it still holds true:
Jo beet gaya wo kal ka sach tha
Jo ayega wo kal ka sach hoga
In do kal ke beech mein
Ek aaj ka sach hai
Wahi jeena hai
Wahi sach hai...