
How should it be written?
In general though, there are guidelines that can be followed by so that the letter will be received more positively by the aggrieved party.
Letters written at the height of emotional distress should be crumpled and thrown away, even even burned. You can surely that the contents of the letter will do not nothing to improve the already broken relationship.
Before writing a letter, it is best to compose your desperate.
Definitely not right after the break up. If you feel as hurt as you do, then probably your ex feels the same way.
So it is better to wait. Timing is a key element towards a reconciliation.
Ask for, sometimes you make, then making making promises at this point will only remind him why you two broke up. Instead, agree with his decision and be honest. Ask for his forgiveness and then ask him if you two can try to make things work out.
Still, if you still love your ex still, then it is worth trying to save your relationship by writing your relationship by writing a letter. Just make sure to follow the above guidelines.

