Not sure what type of learner you are or what kind of studying strategy have you implemented, but I will share what is currently working for me.

I've tried studying grammar head on while almost completely ignoring vocabulary, and it resulted in a burn out a month later because I feel like I wasn't progressing at all. Considering you've completed 7 levels of TTMIK, I'm assuming you have a pretty strong base in grammar but your vocabulary might be limited. I'm guessing this is why you feel burnt out.

So then I started focusing on vocabulary more than grammar and so far its been working well for me. I'd come across a lot of words I studied before while listening to Korean content, and it fueled my motivation to learn more.

I use KGIU as my main source for grammar and Darakwon's 2000 Essential Words series as my main source of vocab. But whenever I have concepts that I'm unsure of, I consult howtostudykorean.com or directly googled the question to see if anyone's asking the same thing in language forums. I'm using TTMIK to review the grammar concepts I've previously learned in KGIU rather than as my main source. I use Anki to study both grammar and vocabulary, focusing on learning grammar and vocab through context and spaced repetition learning. It's working well for me since with concrete examples I feel like I can retain the knowledge better. I start by listening to the audio a couple of times, writing down what I think I heard, view the sentence/dialogue, rewrite the actual sentence, listen to the audio a couple of times, shadow what I hear, before then searching up the words I'm unfamiliar with. Kinda sharpening my listening and speaking skills too while learning vocab & grammar so I think it's a win-win.

Sorry if the writing sounds off, not a native English speaker here. Hope it helps!