Any tips on how to do that? Over the last year or so I find that I have lost passion for both my job and my side-projects. While I used to be happy working 60-80 hours a week between my job and side-projects, I now find both of them mundane and can't pull off such focus. With side-projects it probably boils down to not finding success...
In terms of success: I have dozens of side projects lying around, some of them educational, some practical, most unfinished.
It is completely fine, even beneficial to do so. At work you are already forced to finish and maintain stuff. Giving yourself some free, playful space balances this out.
Also in time some of those things trickle down (quasi) to your day job, or at least it has for me repeatedly. Not in the exact form I was expecting, but in tangible ways nonetheless.
There are two things that eventually keep me “on track” when I have a low phase: reminding myself that I’m a creator with ridiculous power at my fingertips is one. I keep a collection of notes with interesting and fun ideas (together with a friend). The other is more like a safety net so to speak: I seek long term financial security. This is one helps especially when I think about people close to me and how I can be strong for them.
If you can't name one important outcome for your job, maybe it's time to change jobs. OTOH, if all you lack is directing your attention to these important outcomes, I'd recommend some rituals like meditation.