Well, now that the clickbait-ish title has done it's wonder, I'd like to draw your attention towards the fact that my rating has had a +28 aggregate difference over the course of 3 months.

This perturbs me during the middle of the night and with a slight hint of melancholy, I ask myself this. Has my performance/ mental capacity reached it's zenith? What am I doing wrong?

For the former question, I'd like to believe otherwise. About the second one, this graph should be the answer.

Some wise words: If you're currently rated X, you should be focusing more on problems rated [max(X, 800), min(X + 200, 3500].
Now the question arises, why should you be bothered? Well, in all truth, you shouldn't. This is kind of a plea, to put it correctly, not just for me, but for others who might face similar issues. Lately, I've been having an awful lot of trouble solving problems rated 1800+, while problems rated 1600 are a breeze. The transition from 1600 to 1800 seems to be a herculean task for me. Am I lacking some prerequisite? Should I take a break from actively participating in contests and transition to classical problems?
I've been following A2OJ ladders and CSES hitherto.

TL; DR — What should be my course of action to have a reasonable chance of making it to CM?

Here, you'll find links to some useful blogs that may help your case.
https://codeforces.net/blog/entry/66909
https://codeforces.net/blog/entry/75662
https://codeforces.net/blog/entry/83267

PS — Apologies if the blog isn't in accordance with the title.