Always learn something new
Here's the thing. If you're not moving up in life, you're moving down. Same thing with our brains: If you are not learning new skills to keep your brain fit, it doesn't stay the same; it deteriorates.
Our brains need to be exercised. They need to learn something new; they crave it.
It doesn't really matter what skill you learn - it might be a new language or juggling - but it's important always to learn something. Otherwise, our brains get bored and weak.
So, it's not just that you learn a new skill; you also make your mind stronger, which in turn affects everything else you do.