Based on (recent & ongoing) personal experience (which luckily includes not having to work, still getting full salary and therapy/shrink) and learning from that - longer break is obviously good, though likely not enough in longer term.

Exactly that combination of "you care deeply about the area you are working in" and "hard to turn off" (even with less of "very ambitious company") - will eventually bring you back to the same situation, unless you change habits/approach/etc.

Instead of focusing/pushing for "not tying so much of myself to my work/current company" and "motivation" - perhaps it's better to focus on training yourself when and "how to turn off" and not slowly drift towards old habits?

And I think I know what you mean by "depression hits pretty hard and you stop doing things for yourself due to lack of joy/seeing the point in doing anything". Though in my case I realized that it originally started from myself feeling guilt where I was nagging to myself how I can't do whatever fun thing while there was some other work thing/project where I thought I'm behind.

So slowly over time that guilt made fun things less fun, and combined with stress started to skew perception of how productive I am, and how long something will/should take ...etc. Eventually that skewed perception spilled from work to personal life - so for those things/projects that were still at least somewhat fun/enjoyable I also started to be annoyed by them taking longer than what I thought they should take.