YES, the diagnosis was life changing for me. Now I can contextualise things rather than just randomly thinking I'm shit at all sorts of things.
Then another step was learning more about the disorder and being able to compensate for my difficulties, guilt free, rather than constantly beating myself up "Why can't I just remember this? I should be able to remember this." Well no I actually physically can't. So having a massive fuck-off visible reminder is a compensation I can live with.
Next getting medication and treatment helped. I had a big gap here due to pregnancies. The medication hasn't helped as much as the knowledge aspect though. So try not to get too hung up on this.
My top resources are:
Dr. Russell Barkley - he has some books plus talks on youtube (the best) - really really long, but I put it on while I was doing housework etc which seems to have a dual purpose, incentivising me to clean up while allowing me to focus on something just mindless enough that I can actually listen to the audio. You don't need the visuals as the slides aren't shown anyway. He's amazing, he really "gets it".
Youtube channels - How To ADHD, College Info Geek. The first one has short and snappy videos on various ADHD issues. The second is more of a general motivation/organisation tips channel but I find his methods very ADD friendly.
Reddit r/ADHD for the interesting discussions and helpful info.
Avoid:
ADDitude online magazine, it's full of unhelpful stuff these days. Understood.org is much better but aimed at parents of children with attention issues, not adults with ADHD.
Random facebook groups for ADHD. They are often manic and full of drama. I've never been able to cope with one for very long.