If we all live on the principles of love for humanity and not through our selfishness these of kind of experiences and life and love would flourish.
What is love for humanity? I think it is wanting better for others over yourself and your own needs.
Unfortunately many people are just that which is selfish and can't see a rare connection or chemistry or even that spiritual connection because they are too busy thinking about their own needs and own self. They let go these kind of special connections with people and friendships because they are too busy thinking about their own. But at least you know then what they are about as painful as it can be to find out sometimes.
I think you just have to be strong, brave and stay true to who you are even though it sucks to lose these type of connections with people who you loved or still love.
I think just love without expectations if you truly feel like this.