Verified answer

You're probably sad Becuase you remember happy times with her, but happy becuase those happy times were over and you left so you could find someone better.

A good approach on how to forget someone fast is by reversing the old good memories. Using this approach you forget about all the good things and focused on their weaknesses. I know this process sounds weird but I don’t see any other way to put it. Just visualize all what you've went through because of them, all the pains and social tortures because of them, how fruitful your life would have been today if you never knew them. just think of any!

Depending on your background and how your relationship was, you're obviously depressed because your relationship is over, and you're happy because... maybe... you think that she'll be happier with someone else or that you're free?

Some people are just naturally boring, and you may be one, so you'd figured that she'll have more fun with someone else? Or, you may not be financially stable enough to support her?