I just want to say that I'm in a similar position to you. 32 and divorced my wife a couple of months ago. We had gotten together at 18--I had lived with her my entire adult life, excepting college. Still not completely sure it was the right decision, but I had nagging unhappiness in the relationship that I couldn't seem to solve, even with personal and couple's therapy. I have to remind myself how lonely I felt in my marriage sometimes... solitude can be better than a feeling of rejection or alienation.
This is just to say... it sucks. It's really hard. It seems to get a little bit better over time, but at least right now, I still find it really hard.
Some things that help:
1. Claiming the space you live in. Nest. Get some art you like. Put up photos that remind you of the significant relationships you still have, that remind you of good times with others.
2. Exercise. Whenever I'm having a particularly hard day, exercise is a huge reprieve for me. It saps whatever anxious energy I have and channels it into the movement and effort.
3. Observing yourself, the thoughts that crop up to you. "Oh, I'm having thought XXX again. I'm going to put that down for now." The more times you do it, the more it will occur to you that you can. Focus in on your senses, how your body feels. Often, when my mind is anxious or lonely, my body is feeling fine, and I can take some comfort in that.
4. Plans. Make plans with others. Lean into your friendships. Reach out to people more frequently. And, importantly LEAN INTO VULNERABILITY! If you're a man, like me, you might have put a lot of your "intimacy" eggs into one basket--your partner. Try to build these kinds of relationships with others. It won't always work, sometimes you'll face implicit or explicit rejection, but when it does, you'll find your friendships deepen. A lot more people are looking for this than you might expect.
5. Creative and emotional outlets (related). Journaling helps to ground, and somehow the act of writing to myself makes me feel less alone. Poetry and music have been great for expressing some of the pain. The act of creating can be very satisfying, and it's a solitary activity, for the most part.
6. Do nice things for yourself. Keep your place looking nice. Buy yourself things you might want. When you cook dinner, put out a place mat and eat at the table and light a candle--do things you would have done while you were partnered. Treat yourself like you're your own partner.
7. Read things that keep your mind engaged. I don't know about you, but one of the worst things about being alone for me is a tendency to ruminate when my mind isn't busy. Go over regrets, what I could have done differently, whether I made the right decision. One of the best ways to avoid this, for me, is to have books I'm reading that engage my brain when I'm not busy, in thinking over the material that I've read.
Some don'ts:
1. Rebound. I hooked up with a good friend about 2 weeks after divorcing. It got intense quickly (there had already been feelings) and then it crashed and burned (all within a month). I wasn't ready; she wasn't ready. Now we're trying to renormalize back into friendship, but it seems some damage was done. And now I'm carrying two losses in a way that's confusing and just amplifies things. That said, I had received this advice on all sides and didn't follow it... so why would I expect anyone else to? All this is to say, it's probably good to be "okay" with being alone (even if you don't want to be forever) before launching into something else.
2. Careful with substances. It's easy to get into the habit of drinking a bit every night (or at least it was for me), though tbh this had become a problem before the divorce too, since it was occupying me so much... But even in reasonable amounts, it adds up, makes your mood lower, makes the process of moving on and building a new life harder. I imagine the same applies for weed or practically anything else.
3. Social media. Looking at pictures of happy couples, seeing all the things others are doing, or brain rotting watching reels--none of these will make you feel better, but an app on your phone is super easy to reach for when you're feeling lonely as a form of dissociation.