I'm 23 and took an interest in stoicism a few years back. I have to admit I didn't fully grasp the depth of it at the time, a lot of my understanding was more surface level. However having knowledge of the concepts and ideas of the rational mind from stoicism, and the idea of the differences between thoughts and feelings and our connections to them from mindfulness have both been things that I notice when I'm going about my daily life.

For instance there have been times where my mind has run away with thoughts and feelings and I've noticed that and just been able to let it go. Each time something like that has happened I've often had a feeling of 'Oh, that's what that meant.', having an awareness of the concepts of philosophy and the knowledge of people who have thought about these things before us can allow us to notice the same things within ourselves a lot easier.

I think it's worth learning about quite a lot of different forms of philosophy at a younger age, it'll allow you to be more conscious of what goes on in your head and generally understand yourself better. One thing I will say is don't try to convince yourself that you understand, only time can cement that understanding.