advice

does anyone have advice on just letting go?.... it's so hard for me to let go because I just hate being alone and I hate knowing that I opened myself up to someone and gave myself to them all for nothing. it's so hard. (And I am not talking sexually, we did not have sex. I mean I just literally gave myself to him and would pour my feelings out to him and just allowed myself to be vulnerable when I NEVER do that with anyone. and I feel like I shouldn't have. )