Will you help me get rid of these negative thoughts?

I asked this question about changing my life a while ago. It helped a lot, and while there have been difficult patches, I’m on the right track now.

I’m getting ready to adopt a puppy which will hopefully grow up to be a therapy dog. More specifically, a dog I can take to schools teaching children with conditions such as autism. I am also, once the pup can be left home alone for short periods, going to study biology.

I have finally managed to find out what, exactly, I want to be doing. Last week, though, I suddenly started having regrets. I never have regrets, and I’ve never even understood the concept before. Suddenly, though, I keep thinking things like, “If only I’d gotten started two years ago.”

Pointless, of course. How do I stop these feelings? Do you think it’s fairly typical to go through a period of not knowing what to do with one’s life?