If you find yourself in love with someone who does not love you, be gentle to yourself. There is nothing wrong with you. Love just didn't choose to rest in the other person's heart.
If you find someone else in love with you and you don't love him/her, feel honoured that love came and called at your door, but gently refuse the gift you cannot return. Do not take advantage, do not cause pain.
How you deal with love is how you deal with you, and all our hearts feel the same pains and joys, even if our lives and ways are different.
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 to assess blaim, let it go. There is a reason and 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 to accept it for all its mystery when it comes into your life. Feel the way it fills you to overflowing, then reach out and give it away.
Give it back to the person who brought it alive in you. Get it to others who deem it poor in spirit. Give it to the world around you in anyway you can. There is where many lovers go wrong. Having been so long without love, they understand love as empty places that will be filled by love, and they begin to look at love as something that flows to them rather from them.
The first blush of new love is filled to overflowing, but as their love cools, they revert to seing their love as need. They cease to be someone who generates love and instead become someone who seeks love.
They forget that the secret of love is that it is a gift, and that it can be made to grow only by giving it away. Remember this, and keep it to your heart. Love has its own time, its own seasons, and its own reason for coming and leaving. You cannot bribe it or coerce it, or reason it into saying. You can only embrace it when it arrives and give it away when it comes 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 has been and always will be a mystery. Be glad that it came to live for a moment in your life. If you want to be happy, be!