in life...
what is, is.
this simply means that what has happen cannot be changed. you cannot change something that has already happen.
so i think it is best to leave the past to the history books... the present for now.. and the future with God.
refer to the past to see and learn mistakes and not to make the mistakes again. live the present to the fullest... you will not live the present twice... use the present to shape your future.... but leave the worrying to God.