Perhaps it would be helpful to note what a lack of self care looks like?
My daily routine usually involves waking up, skipping breakfast, going to school (if I wake up early I kill time by doomscrolling on my phone), coming home, laying in bed (more doomscrolling), eating something, doing school work, and then going to sleep. Most of my free time is wasted on my phone and I'm usually stressed about at least one thing.
So what's missing? Well I could spend some more time socializing, gaming, treating myself to meals I enjoy, etc. Personally, I have anhedonia so finding things I genuinely enjoy is difficult, which makes self care difficult. But self care isn't just about meeting your basic needs, it's about feeling good after you do it. It's a little break from everything that's stressing you out.
As someone that's done a lot of therapy - self care is usually recommended because you're not happy with how your life is. Think about what prompted that conversation. Did you describe an unhappy lifestyle? Something (or several) that has been stressing you out recently? Now think about what could help you feel a bit better, or at least give you a (healthy) break. It could be a bubble bath, visiting a cat cafe, going for a swim, etc. There are countless ideas online but it's important to find something that changes how you FEEL. As other people have mentioned, self care is an important part of your daily routine.