I live in a very small house, about 500 sf, but it's not laid out very well so it feels like less. There are NO closets, even in the bedroom, and the kitchen has two drawers and four small cupboards for storing everything (food, utensils, pots, dishes, etc).
Here are some things that helped me adjust to it...when I moved in, I knew I was downsizing, so I took a really critical look at all my belongings and got rid of a lot of them (about 20%). I donated all of it. I have never felt so good, and even now I feel there are some things I could get rid of.
Have a private space for yourself somewhere else, if you can. I am lucky enough to have a large yard, and I look at that as part of my square footage. I set up some private, secluded areas for me to relax in, read or pray or whatever.
Realize that just because you have no room, doesn't mean you have to give up features. Find ways to "multitask" a space. Don't have single-purpose devices, items, or spaces.
Hope you can use any of these tips...