How to Not Backslide

First, just want to say I'm really glad to see this community growing. What a great game to see revived!

My question is how to not backslide as a player. I've peaked at a little over 1700 ELO on Steam, but on average I'm probably more like 1650. And based on recent games, my ELO is now actually closer to 1600 and is on the decline. I've played multiplayer for about 2 years.

I feel like I've completely stagnated. And honestly, sometimes I feel like I'm getting worse rather than better, at least relative to the average level of play on Steam/Voobly. I know there is plenty of very helpful material on this sub, Youtube, Twitch, etc. (and thank you to those of you who put those materials together!). I've watched the instructional videos, I've played the interactive BO tutorials (thanks Cicero!), and I've tried to watch replays of my games to understand where I went wrong and how to improve. I also watch pro games, read the written tutorials, and feel like my general game knowledge is high. But I seem to keep going on losing streaks where I just can't get a win, even against players that are lower ELO than I am (which I understand is an imperfect measure of ability, but point being players who in theory I should be competitive against). It gets really disheartening.

How do you keep your morale up when you can't seem to get a win? If anyone relates to my struggle but figured out how to become a more consistent/better player: how?!?! It seems like everywhere I read, people consider <1800 HD "noob" level, but I can't seem to maintain even 1700 ELO on HD, much less get to or maintain 1800.

FYI: I'd say I have a good early game and solid late game for my ELO. Where I really struggle is mid-game.