One of the better 1 word answers this year. :-)
Because it hurts
Because rejection HURTS. Especially when you've been led on. It feels like there is something wrong with You- even if that is illogical, the heart does not always agree with the mind.
And if your mind makes all of the decisions, you become far too cold to be truly happy in this world. There has got to be an even balance.
Because if you've been rejected you think you can't be loved and you tend to bring the worst out in others..... self-fulfilling prophecy.
It hurts ego m self esteem !!! We wen its "true " fear of rejection will go !