I got the second COVID shot last week, and I felt like hell for several days. I didn't practice at all a couple of days, but on other days, I at least did some open string bowing, or played around with stuff that I like, rather than doing actual planned practice (and I've been planning my practice week on Sundays for a few weeks, now, which I find I really find useful).
I practice in the mornings, before work, because if I don't do it then, I'm likely to not have time or inclination to pick up my instrument in the evening. My SO likes to watch TV at night, so it's more frequently that I don't have time in the evening.
If I'm not feeling it, I'll "eat my vegetables" and at least tune and do open strings and work on one scale. By the time I've done that, if I'm still not feeling it, I'll quit for the day, but usually I'll keep going. If you just tell yourself you're only going to tune your violin and do something for five minutes, then stop, then at least you've touched your violin, and if you do feel like stopping after that, then you've "earned" it. If you feel like continuing, you can still continue.
For me, I feel like I need to at least tune and bow open strings every single day, so I keep the habit going. If I get at least that far, I'll give myself a pass for the rest of the day, and I can manage even that unless I have a bad migraine or am really sick.
Now towards the end of this month, I will be out of town for a week and a half, and will not be able to bring my violin with me, but I will probably still do some sort of ear training every day, with an app or three.