How to enjoy alone time?

Not sure if this counts as a social skill, but I (30F) really struggle with alone time.

I’ve lived alone for several years throughout my life, and I always kinda hated it. Currently I live with my boyfriend. Since we moved in together, my well being improved dramatically. Just knowing that he’s at home with me, or that we’ll see each other for dinner, makes me feel so much happier. We have a lot of fun together and it’s a great relationship overall.

Unfortunately, every time he’s not around, I get really sad, especially if I’m not busy socializing with other people. I lose motivation to do basic things like go outside or clean the house. This worries me sometimes.

I travel alone a lot for work, and I might even have to relocate abroad by myself for a year. I don’t want to be miserable every time he’s not around. I really want to learn to be relaxed and happy spending time by myself.

I enjoy movies, books, videogames, and photography. I also enjoy cooking and working out. But when I’m alone I often just spend hours watching YouTube or scrolling reddit, which ends up making me feel even more sad.

Do you have any strategies or suggestions on how to approach this issue?