Why girls are leaving boys

Women systematically, date, chase, love, throw themselves at the mercy of men, in spite of the fact that they feel like shit when they are around them. And whilst there are some men in the scenario above, there are also quite a few men that don’t know what to do with the love of a good woman, get freaked out, and run off, turn into stone emotionally, stall on commitment or even shag someone else. Feeling good or The Pleasure Principle for some guys means that they either freak out and run for the hills when it’s good or shag as many people as possible to get as much of The ‘Pleasure’ Principle as possible. Some men just don’t know they’re born, and some women, in fact many women have misguided insecurity that drives their relationship choices which means that they believe that part of loving is not feeling good!
Reasons Why Girls Leaving Boys
Pleasure Principle
“When you are constantly freaking out on a man for what it is about him that freaks you out, you quickly turn into one of the people that it DOESN’T FEEL GOOD to be around. And this has a huge impact on whether or not he wants to invest more time, effort, and energy in you and your relationship. Or if he will decide to give up on trying to fix what’s going on with you so you can both feel good together.”
Emotional 
if a woman is consistently negative and emotional… and can’t get herself together even when a man tries to explain things and comfort her… then a man isn’t going to think that things could be any better in the future together.”
Feelings Of Attraction
Attraction is important in a relationship and this should be a mixture of emotional and physical, however let’s not confuse this with expecting to have constant fireworks. What keeps a relationship going, what real love is driven by is a mutual attraction, trust, respect and shared goals and interests. To read this reason of Christian’s answers the question for men as to why they are ‘misunderstood’.
Neediness of Codependence
A man wants to be with a woman that brings something better to his life, not take away his time, energy, and emotional “stability”.

So when a woman doesn’t have much going on for herself in her own life a few things happen. First, she focuses on her relationship too much as her source of happiness or unhappiness.
These of the main reasons girls leaves relationship.