Only really in terms of- we can't change the past. All we can do is try and mitigate 'bad' decisions moving forward. I guess the problem is that: Having made choices we regret, we can start to think everything is now doomed to failure, so, we don't have the motivation to try to rectify things. I guess when I lack motivation- which is most of the time, I just try to tell myself that if I don't get off my arse and do something, matters will only get worse.
Plus, it's a cliche but- we learn by making mistakes. We may learn more in fact. I've done and left several jobs in my time. Were they a mistake? Not entirely- because I wouldn't have truly known I'd hate them without trying them.
Plus- another old chestnut: 'No point in crying over spilt milk.' Really though- you can cry about it if it helps but- don't just leave it spilt on the floor to turn and stink. I suppose I've always felt the key was to keep trying. If it fails, try something else. That can be incredibly difficult though, I realise.