Something I learned a long time ago was that doing anything creative, be it writing, drawing, etc, is like doing a workout for the artistic parts of your brain. Just like working out irl, you can't go from 0 to 100 because those parts of your brain aren't strong enough. You have to start with doing something small, and even if you're just drawing the equivalent of a 5-pound rubber weight, that's still something that eventually builds towards a goal. And the exact same as working out, there's no trick to it either. You draw, you give yourself proper breaks/rest, and you start to build up to eventually doing large pieces, and eventually a full animation.
Now, I said there's no trick, but it's not entirely true, because the real trick is to keep yourself consistent with it, and that's tricky. Not consistent like "I have to draw on this day at this time for this long," but keeping it in mind and doing something about it. Sometimes you don't feel like drawing on a day you normally do and that's fine, a lot of times that's your brain telling you that it can't today. But eventually it becomes a habit to skip and be lazy, and once you get into the habit of it, you sorta spiral and put yourself down for not drawing, which only perpetuates the cycle (speaking from experience here). So you just have to start doing it, and the path that leads to bigger and better works starts to open up.
Also fuck outta here with that "im 18 and my chance has passed" bullshit lmao, unlike the working out metaphor, there's never a point where you're too old or too weak to make art (and if there was, it'd be nowhere near 18).
And if you see someone even younger than you that's better than you, don't take it as a negative reflection on yourself. There's always gonna randomly be some child prodigy who is just straight up better than someone who's 40 and been doing art their entire life. Sometimes random luck and raw talent are a bitch rofl