If you have gotten to 1800+ rapid, then you've already overcome two of the biggest stumbling-blocks that beginner and intermediate players face - poor situational awareness and poor tactics.
Time to learn some strategy?
Try reading my posts on the first two or three pages of this thread (especially posts 7, 8, 9, 10 and 12), and playing over the first three sample games... paying close attention to the notes to the moves.
GM Larry Evans' method of static analysis - Chess Forums - Chess.com
I started playing chess 4 years ago, as an adult; playing and studying some periods more, some less and some nothing. I reached a rating of 1800 + on chess.com (10 min blitz) and on lichess I'm stable over 2000 (I play 15/10 there), but never over 2050 until now.
I have a decent opening knowledge (for my level) and I studied basic endgames. I see that most of my games are still decided by a tactical shot, so I recently decided to improve my calculation and visualization, training around 40 min/1 hour everyday (I started this routine 1 month ago, my time for chess is limited). I analyze my openings after the games solidifying and expanding my repertoire (I think I spend for the openings less than the 10% of time that I dedicate to chess) and learn strategy mostly from videos (I'm a fan of Naroditsky's speedruns) or videolessons.
I'd like to ask to stronger players (particualrly adult improvers) who were at my rating not decades ago, how they broke let's say 1900/2000rapid here or 2100 on lichess and what was their main chess training at this level. Of course chess for me is just an hobby but I'd like to slowly improve.
Thanks in advance for your answers