If you're in university, then you're probably in a place that has resources that can help. Take advantage of them. For example, you may have access to an occupational therapist who can help you improve how you organize and schedule your work, create effective workplace, avoid distractions, etc. Medication may also help, but it works best in conjunction with active behavioral changes.

There is no substitute for medication. For me a life without medication is a life of hating myself for not being able to do trivial things.

I tried all of those things you mentioned for over a decade and was often driven to tears trying to do simple things. I never did assignments for courses etc, causing some of my grades to stay bad even though I did great on the tests since tests kicks up your adrenaline making it easier to focus. Not because I didn't care about the grades but because I simply couldn't do the assignments. Then I got medication and suddenly everything in college and later work just became trivial. I stay on the lowest dosage and that is still enough for me to stay at normal levels of focus where I can program for a few hours a day when I need to do it to keep my job and earn money.

So, since medication has been so life changing for me I really hate when people say that you can manage ADHD symptoms just with lifestyle changes. Maybe in some cases, but many people absolutely need medication and discouraging such people from receiving it will ruin lives.

Sorry, I didn't mean to imply that it's possible to treat ADHD with just behavioral changes or occupational therapy. That wasn't true in your case and it wasn't true in my case either. In my case, medication has been eye-opening and life-changing. When I went back to school, however, I also found it helpful to work with an occupational therapist to set up specific strategies for staying organized, keeping up with assignments, effectively using my studying time, and minimizing distractions. Working with an OT who understood ADHD was different from just trying to adopt general studying strategies and it really helped me succeed in grad school. If the parent poster is in university, an OT may be an available resource.

If I regret anything, it's not getting diagnosed until I was in my 30s. I wasted years of my life doing poorly in school, being depressed about it, blaming my performance on being depressed, and then dropping out of school. I eventually graduated, only 10 years late and with a 2.2 GPA. After getting diagnosed and treated, I went to graduate school and finished in the top 15% of my class with a 3.7 GPA. I think I've redeemed myself, but I won't get any of those wasted years back.