Have you tried Journaling? Maybe you can write him letters while he's gone.

all my coping mechanisms are almost all escapism . listening to podcasts (my main ones atm are 'last podcast on the left', a very funny true crime podcast and 'distractable' with Markiplier and his two close friends, bob and wade, where one hosts and gives a topic, and they tell personal stories about that topic and almost always get distracted..) drawing, usually drawing things i feel, small stories, characters, clothing, anatomy, and poses. roleplaying, as my own characters or other fictional characters with friends, their characters or a fictional character. journaling, poetry, song writing, playing guitar, scrolling down reddit, instagram, twitter, going on discord, etc... also tv! movies, films, shows, youtube, i spend lots of my free time with my cat watching random shit on youtube, lol . try also going out, go someplace you think about going to, window shopping, trying clothes on and not buying any of them, and maybe bring a friend or more with you. i really hope this helps!

My boyfriend just recently went to NTC (Ik it’s not the same sorry) but what I do in the mean time is try to keep myself busy with my hobbies, work, and friends. I also reread his and I messages so I feel I lil less lonely without him. I also text him even tho I know he’s not gonna answer it’s just the idea that he’ll respond when he gets back. I also look at old videos and pictures we have together. I hope all that helps

It won’t be easy at first cause you’ll miss him. Try to enjoy your own company. Reach out to friends. Do Art and journal. Listen to your favorite music. Watch Netflix. I hope this helps.

Humor...bad bad humor. 😥