Age doesn't matter: an open mind does.
A goal without real consequences is wishful thinking. Good follow-through doesn't depend on the right intentions. It depends on the right incentives.
It is possible to become world-class, enter the top 5% of performers in the world, in almost any subject within 6-12 months, or even 6-12 weeks.
What you study is more important than how you study. Students are subordinate to materials, much like novice cooks are subordinate to recipes. If you select the wrong material, the wrong textbook, the wrong group of words, it doesn't matter how much ...
As you stumble and learn, stumble and learn again, resolve to talk to yourself as if you were your best friend. So no "What a #?%$@ idiot!" when your BFF smashes an egg on the floor, m'kay? Be cool, like the Fonz.