Whenever you start doing something after a long pause from it, you generally suck. But since you've been doing it in the past, you're don't suck like a beginner, you just suck cause you're out of shape. And that's why the first few times you improve rapidly. You go from zero, nothing, to almost-showing-signs-of-ability. In short, the steep curve. Today was my third time playing and I'm about half way to the level I once was at my peak.
Of course, after reaching the almost-decent level, the steep curve ends. Then comes the polish phase, which takes forever. I played football for 10+ years and I would have maybe 1 games in 10 when I felt it went off like clockwork. The rest of the time it was always part good, part not-so-good. And always working on the polish, repeat ad nauseum. Tennis is looking really good at the moment, I've drawn up a schedule to play twice a week and there seem to be more people out there interested in playing. Today was a beautiful 2 hour session, it started to drizzle toward the end, gorgeous.
My game still needs a lot of work, I'm slow and my reflexes are off. But once I get the basics to a half decent level, there'll be plenty of time to polish, polish, polish.