Some thoughts... despite my RHP rating struggling badly...
Find your own path. There may be some common advice that applies to many players, but the more one progresses, the more their training has to be specific to their needs. Thorough and honest analysis of one’s own games should provide what the weaknesses/needs are. It’s possible that in terms of weaknesses, a given 2200 and 1900 player can have more in common than two 2200 players or two 1900 players.
Consider a coach. Yes, they are usually costly. I can’t suggest any way round the cost, but I will say that working with a good coach revealed many fundamental flaws in the way I play and train. For the last year I’ve not really used a coach. Prior to that I had consistent help for a couple of years. My OTB improvement has recently halted and part of my plan to tackle this issue is to use a coach again (via ICC and e-mail).
Don’t fool yourself regarding what hard work actually is. Long hours is not necessarily proof of hard work. Reading many books is not definite proof either. Playing higher rated players can be done without applying full effort. Etc. etc. Real hard work is when you genuinely stretch your abilities and push your limits. You should feel strained during the training, and probably tired afterwards. Compare doing a hard physical run as opposed to a walk in the park; duration alone means nothing.
Don’t equate “improvement” with “learning more”. More often the real problem is fixing our current assumptions, prejudices and habits regarding what chess is and what it requires to play well. However, it’s far easier to pick up a book than try to change a habit which has existed for years. But the latter is often more important.
Try to forget about ratings. If you want to assess your ability or improvement, rather than look at ratings, pick out your recent games that you are proud of. Imagine you have to present these to an audience. When you start using this attitude, it encourages you to take pride in every move that you make, rather than thinking about the end result.