Physical Danger
It's less of a danger and more of a certainty. Your body will break down, sooner or later. Just keep your fingers crossed (but not too tightly; you've got a tournament tomorrow) that it doesn't happen while you're still in your prime. It isn't uncommon for a knee or an ankle to go out, and while there are more surgical options today than ever before, most of the time you simply won't ever be the same again.
Aside from that, make sure that you're never within throwing distance of John McEnroe when he's holding a chair. He's not afraid to use that thing.