In order to start a new successful relationship, you have to let go of the past. This means letting go of the misunderstandings, the bitterness, the arguments and anything else that has gone on in the past.
It is impossible to make a sweet drink if you use bitter grapes. And what is the best way to get rid of a sour taste? To introduce the opposite which in this case is forgiveness, love and appreciation of both each other and of yourselves for getting into this situation.