Putting 4 down for bedtime is not easy. We stagger bedtimes because 3 of my kids sleep in the same room. My newborn has a window when he goes to bed, but not a set time yet. I am with my kids from the second they wake up until the second they go down. I’m so lucky to WFH but it’s also exhausting dealing with the kids nonstop from 6am to sometimes 9pm or later.
My husband helped me last night and I’m so thankful because the older boys have been rough lately. (He works a very physically demanding job and is usually asleep when they go down). My kids have their dream sync light and when it goes on, they know they need to wind down for bed. My little guy sleeps in my room right now so I bought a second dream sync light for him. I’m a no noise and pitch black sleeper so this has been an adjustment for me 
I get time to myself when the whole house is quiet. It’s usually after 9 pm. I get myself a snack, a small protein shake, put on my pumps and I watch Shark shows on HBO max. (My next live I will be a marine biologist). Sometimes I do watch crime shows but right now I’m into the sharks. That quiet time helps me wind down for bed myself and lets me be /me/ for a bit 
Motherhood sometimes means putting yourself last. It won’t be this crazy forever but a routine, products and something to look forward to after the kids go to bed gives me some peace. I’ve adjusted to having my quiet time late at night.