I do not think that its just marriage as such that you want. Or else you can certainly marry with someone who is not a good marriage material, but wants to be married too. So, I guess you have some standards and you do not know any woman who both meets those standards and is interested in you.
Why to be content being single? Because we are born single, its our natural state. If you are not content with your natural state, you have a problem.
Build yourself up, your life, strength, mental state, career, hobbies, move to place you want to live in, have a purpose in your life, achieve success in various areas. If some attractive and good woman will want to join your successful journey and help you with it, fine, if not, fine too. But do not center your life around it and do not wait for it.