If you find yourself in love with someone who doesn't love you, be gentle with yourself. There is nothing wrong with you. Love didn't  choose to rest in another person's heart. If you find someone else in love with you & you don't love him/her, feel honored that love came & called at your door, but gently refuse the gift you cannot return. If you fall in love with another, and he/she falls in love with YOU, and then love chooses to leave, do not try to reclaim it or assess blame. Let it go. There is a reason & there is a meaning.
You will know in time.
Remember that you DON'T CHOOSE LOVE. LOVE CHOOSES YOU. All you can really do is accept it for all it's mystery when it comes into your life. Feel the way it fills you to overflowing, then reach out & give it away. Give it back to the person who brought it alive in you. Give it to others who deem poor in spirit. Give it to the the world around you in anyway you can....
This is where many Lovers go wrong. Having been so long without LOVE, they understand love only as a NEED. They see their hearts as empty places that will be filled by love, and they begin to look at love as something that flows to them rather than from them. Remember this, and keep it to your heart. "LOVE HAS IT'S OWN TIME, IT'S OWN SEASONS and IT'S OWN REASON FOR COMING and GOING." You cannot bribe it or coerce it, or reason it into staying. You can only embrace it when it arrives and give it away when it come to you. But if it chooses to leave from your HEART or from the heart of your LOVER, ''THERE IS NOTHING YOU CAN DO and THERE IS NOTHING YOU SHOULD DO.''
LOVE always had been and always will be a MYSTERY. be glad that it came to live for a moment into your LIFE. "IF YOU KEEP YOUR HEART OPEN IT WILL COME AGAIN."
Failure is the opportunity to begin again more intelligently.

Love. With it, you are opening yourself to endless pain but, without it, you'll never know which misery is worse.