Don’t do Judo.
It’s painful- T3hPwnisher is right; but in training/practice you’re smashing your body into the earth many many times each session. If the school you’re going to doesn’t have quality spring floors then it’ll hurt, even if you’re really good at rolling through the throws. It’s more a matter of ignoring the pain… Until you have a very spirited session with someone and accidentally get spiked on the head.
It’s very difficult to progress in if you’re a hobbyist- It took me almost 3 years to go from “incompetent” to “barely competent” at the second throw most schools (I believe) teaches you- the shoulder throw, and that’s only because I decided to switch to a lapel grip for the throw, giving me far better leverage. It’s a bit of a cheat though and leaves you open for counters.
Do BJJ and/or Boxing instead. It’s really easy to take people down to the floor if they’re not trained; just trip or shove them while you have their legs tangled up!
BJJ is said to have a better sense of progression even for a hobbyist, and from what I’ve heard it’s just fun to hit the heavybag.