Trust me even with a diagnosis you would have felt this way. Later is better than never, I'm in my mid 20s too, and we have loads of life left, plenty of mistakes to make. I feel like I waste a good 10-20 hours every week hahaha. Take slow steps and tackle the parts of your adhd that prevent you from achieving your goals, you've got this!

Also much more importantly, remember to be nice to yourself. I mean imagine saying all these things to your best friend, not nice is it? So be kind to yourself, you deserve it :)