What happened to 'just do it'?

When I was 19, 29, 39 - I still had the ability to move quickly to do what I wanted to do. This weekend I found that I have constraints that will not allow me to do certain things. They are self imposed. I have become my conscience, whole and entire. My want to do things is still there. My wish to do things is still there. My will to do things has atrophied. Is there anyone who doesn't understand that I'm talking about sex? There was a time when it was as simple as breathing, when it needed no rhetoric, no thought, no emotion, no rhyme or reason, only eye contact. Now, when I am in a place where there is opportunity many times daily, I persist in ceasing and desisting. It is so unfair. I censor myself. I'm not happy about it; but I continue to say no to offers that range from movie and sex, dinner and sex, marry me and sex, to I'll give you all my money for sex. Shouldn't wisdom and self-control make you happy with your life? I know that at this point in my life, no is the correct answer to every option that includes sex without the requisite emotion attached, but it is so lonely.