One of the sucky things about exercise is not exercising and then exercising again

So, I'd gotten up to 18 laps in the pool at the YMCA, in half an hour. That's not, like, IMPRESSIVE, or anything, but it's not EMBARRASSING. I'd gotten up to the point where I could consistently swim laps as if I actually belonged there swimming laps.

Then, one day a couple weeks ago, I couldn't. I just . . . stopped at six laps, and couldn't go further. I don't know what it was -- I'd given blood a couple days before, I'd had terrible nutrition, I was sick, I don't know. I've been having fatigue problems since.

I got back to swimming again, today, and managed twelve laps. Now, twelve is more than six, but it's less than eighteen.

Oh, well. I just have to keep at it, I guess. I don't know what went wrong; I don't know what my body's doing now. I don't know why it stopped working that one day, or how I can get it back, and get further. But I'm going to keep working on it.