How to naturally increase attention span

Hi, I was curious if anyone had any advice on how to improve attention span. I am realizing as I get older that I had much better attention span when I started my career 10 years ago. I am finding some days I really struggle to focus and do creative work. As an experiment, I tried taking one of my friends vyvanse and it really was amazing and I felt like I had the attention span I used to. I would rather not rely on something like that though. Has anyone tried more natural ways? Caffeine is great but my tolerance is sky high now and it is not enough anymore.

Thanks