I've struggled with anxiety issues since I was a middle schooler but they're not near as constant as they used to be. They can get bad enough every now and then though where I start to feel physically ill. Thankfully I've learned how to deal with that via peppermints and medication if I need it. I don't medicate for my anxiety though since it was never unmanageable enough without meds.
I also realized that I had struggled with depression for way longer than I thought, possibly since middle school like with the anxiety. It got really bad a few times and it's the worst feeling because it's a total lack of feeling. At least when I was just anxious, I'd still have feeling. Depression is one of those things I figured I'd be feeling forever, but I've managed to pull myself out of it through therapy and just learning to cope on my own by giving myself things to be motivated about.
I have also struggled with self-harm and intrusive thoughts. Both are incredibly scary and I'm so grateful that they're not a 24/7 constant like they used to be. With intrusive thoughts, I trained myself to strike a balance between letting some thoughts go and challenging others. You can't fully fight against your brain but at times, you do need to challenge your thinking if you want to grow and re-wire any consistantly negative paths. As for the self harm, therapy helped me the most with that and learning how to regulate my emotions. My urges were so hard to understand for the longest time but now I know it was just my natural response to being overwhelmed emotionally and mentally. I have learned to let myself stim (in a non-harmful way) if I am feeling that kind of overwhelmed or I grab a plushie and cuddle it if I have one nearby. Avoiding triggering content as much as possible has helped too, since I used to consume that sort of content all the time without realizing I was just feeding my urges.