I'm sure you've heard the saying that you can't teach an old dog new tricks...but I have two dogs (one is almost nine and the other is almost two) and you CAN teach them new things, you just have to know how. The same goes for humans.
I'm sure this saying arose because we get so stuck in our old habits and patterns that it becomes harder to learn new things, but it is possible. The same goes for learning new things about yourself.
In a way, while learning skills and other external things gets harder as we age, learning things about ourselves gets easier (though it may be harder to accept new things about yourself as time goes on) because your inner growth happens as a response to external influences, so as you have more experiences, you grow more.
We tend to put ourselves in very specific boxes when it comes to what defines us. This limits our ability to expand our knowledge and grow. I hear this all the time from people who are very logical thinkers and work in careers that support that (engineers are a good example). These people often say that they can't do creative things because they are too logical. But the truth is, anyone can learn anything so long as you go about it in the right way.
When you set out to learn new skills, you need to be very specific (the same goes for any goal setting that you might do, specific and measurable). Rather than saying that you are going to learn Spanish, pick a specific goal and a specific timeline. For example, I'm going to learn 30 new Spanish verbs and how to conjugate them in the present tense in 30 days. That is both a very specific skill and a very specific timeline.
You also need to make sure that you practice your skill...daily! I'd say that 15-30 minutes a day is a good place to start. And in order to ensure that you do actually practice, schedule your practice time in daily. If you are learning or practicing yoga or anything else that involves going to a class, this is a little easier because you actually have to show up somewhere. But if you are learning the thing on your own, schedule your practice time as you would if you were actually going to a class to be taught.
Tracking your progress is also important, because that's going to keep you motivated. How you do this can vary depending on what and how you are learning, so you need to find a way that works for you.
Once you've mastered your skill...pick a new one, or continue to improve on what you've just done. The satisfaction of making progress is a great motivator and can help give you momentum to keep moving forward. Going back to the Spanish example, you could pick 30 new verbs to learn, or you could learn to conjugate the previous 30 verbs in a different tense.
Why is this even important? Because so often I hear people say "oh I could never do that." Which either means that they don't want to (which is fine...but just say that you don't want to, not that you can't) or that they aren't willing to try for whatever reason (usually fear of failure). In order to keep learning new things and improving yourself, you need to get comfortable with the idea that you probably won't be instantly good at most new skills, but that's perfectly ok.
When I set out to run a 50K (which isn't technically a skill, but it's a new and different thing that I've done recently), I had zero expectations about how good I would be at it and my only goal related to that activity was to actually complete it. I enjoyed the process of training and I did complete it, but I was not "good" (i.e. fast) at it.
We get so used to living inside our comfort zone that we forget what it's like to step outside of them. But the value of stepping outside, getting uncomfortable, learning new things, being bad at new things, and taking additional steps to become better at the things we are bad at is huge. And who knows, we might learn something new and interesting about ourselves in the process!