The main reason is ego depletion. We feel worthless,empty and rejected. Mind takes rejection as pain.
We have lot of mental thought and dreams attached to person we love. They become our part of thinking schedule, our life. Thoughts about them gives us high, we feel much better about ourselves and our future.
Now some one is snatching part of your mental thought from you! Your comfort, your dreams, your future…
You will feel loss.
My method is no expectations. No future plans, dreams, attachment etc. The moment I want, I can turn you off. Never allow anyone to take your mental space. Avoid their thoughts in the beginning. Try meditation. It is easy in beginning. Once you can avoid any attachments in the beginning, it’s much easier.
Thinking is a habit,same as non thinking!
If you make them your life and some one takes your life…for sure you will die.
Love is a small part of life for most of us. To make someone your life, you need their life too. I’m a businessman in this regard. I only swap lives,not one way.
Secondly as safety measure, I take before I render. Bit selfish but true.