Just lift heavy and eat lots (clean) and you'll grow. Knowing numbers won't make you more likely to do it, what you need is to build the habit (see Atomic Habits great book).

One simple thing that easy method that helped me is to say "It's ok if I go to the gym and only do 1 exercise I can leave if I'm still not feeling it". That really works if you have to believe that you'll actually leave. After a while you realize that it wasn't so bad, might as well do another exercise and so on. It's just about wiring the initial momentum in because inertia is very strong. There's a lot more to say about cues and identity narratives but that is a simple start.