How to stop beating myself up

Hey, I'm not sure if this is in the right section but I am finding life particularly tough at the moment and I don't really know why. I am 24 and have a loving family, some great friends, I'm fairly well-off and I have a job but I am not happy with my life and I am constantly beating myself up for not being a better person, and for not achieving more things.

I've always been fairly anxious in stressful situations but ever since I have worked in a call centre (for the last 2 years) I have become more and more anxious.

With girls I used to think I wasn't that attractive but that I quite liked my personality, so I had something going for me. Now I feel that I have nothing to give and that whatever I try to do will just go wrong.

In all aspects of my life I expect perfection from myself and I'm always dissapointed with myself. It is really geting me down and I feel like it has been ages since i had natural, unforced, fun. I feel like I need to get out of my current job but don't have the motivation as I feel like I will just fail at geting a new job. How do I get out of this cycle?