How to just move on when you messed up?

It was my fault that I feel this way now because I kept trying to pursue her but this girl and I went on a date before and she said after the date that she wasn't feeling any romantic feelings and basically rejected me. she's 23 and im 21. I kept doing things with her as friends but I ended up really starting to like her a lot. I didn't think she was interested still and I was getting tired of playing games so I just told her how I felt about her and if she thought that there was ever a chance of us becoming more than friends. She said sorry but that we are just in very different parts of our lives and she said she's trying to settle down and start a family and that I haven't even started my career path yet. I want to join the military but haven't because Im getting my anxiety problems taken care of first and I've told her that. I mean I do have a job though but I also still live with my parents mainly because I dont see the point of getting an apartment when im just going to be leaving it when I join anyways. She said she knows its not my fault at all. I just feel like shit because I got rejected again and secondly she would probably be with me if I had started my career and I just can't stop feeling regret about it. How can I stop caring and stop feeling regret?
How to just move on when you messed up?
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