It may be childish or fantastical, but I think it's nice to think that some things happen for a reason, even if they don't work out the way you originally had in mind. We're only human and sometimes our design isn't fully thought out or doesn't take certain things into account. But the universe, whether you want to call it that, or God, or destiny, can see things from every angle and see the game 20 moves ahead. For this reason, the universe can arrange things to play out perfectly from time to time. Sometimes, it takes us some time to realize that it was for the best that things happened in such a way.
Pessimists and regretful people have a tendency not to see things as having worked out for the best. Maybe it's self-importance, wanting things to go their way or the highway, or maybe it's just closed-mindedness, that if things didn't go a certain way, they went the wrong way. It's unfortunate, because if you only look at the world from that perspective, you end up missing out on some of the beautiful and amazing, if unexpected, things that happen.
I find regrets to be a waste of time. Regrets mean that you focus on something that happened in the past, and if that is still eating away at you, weeks or months or years later, part of you is being wasted and consumed by something that shouldn't matter anymore. It only still has bearing on your life because you allow it to. While my life has certainly not gone according to any plans I made at any point--eight years ago, I was going to move to New York when I was 18 and be a writer, and that didn't happen--I can't say that I regret anything that's happened to me or that I've done.
Other people, were they in my shoes, might regret some of the things in my life. I spent three and a half years on a degree that didn't help me get a job very easily. But I did get a job. A great job that I really enjoy. It has absolutely nothing to with my degree, but I never expected to go into philosophy after all. I expected to have a bachelor's degree, some more knowledge than I started with, and to be a more well-rounded person, and that's all true. So how can I possibly regret something that put me in a good place in my life, even if it took a little longer than expected? Answer: I don't.
There are plenty of other things that could have thrown me off track and made me regret that they happened or changed me in a way I didn't want to be changed. But even all the bad things that have happened, all the things that went wrong thus far in my young life, put me where I am today and prepared me for other things I would face. They made me stronger, and for that, I can't really regret those things either. Even if they sucked when they happened, I can't really blame anyone for what happened, even if a person was the catalyst that caused that particular event to happen. Blame is a by-product of regret, and if you don't regret anything, you can't blame anyone for where you are today or what has happened to you up until now.
As they say, you can't make an omelet without cracking a few eggs, and sometimes the things that don't go according to plan are the eggs that the universe breaks to help you make your omelet. (That came out so much cheesier than I meant it to, but oh well.) Next time something goes wrong, give it a chance to work itself out before automatically writing it off as the universe being out to screw you over again. That seemingly unfortunate, unexpected event may lead to something great.
Sing in the rain.