Loneliness is a state of mind and has little to do with being alone. You can be with somebody and still feel lonely, and be completely alone without loneliness. If you miss the routine, create a new routine. Find a diner where you can go have breakfast every Saturday morning. Don't expect others to make friends with you immediately, they have no real motivation to do that. Start a conversation with somebody. Ask them to pass the salt. Make a comment about what they are eating, or the traffic outside. If you see them again next week, say hello.

Big things often start as small things. One of my best friendships in college began when I said hello in a lunch line because I mistook him for somebody else. It turned out we had a lot in common.

It sucks.

My work keeps me "unlonely" but only for about 10 hours a day.

Then I go home to my one-bedroom apartment

Loneliness isn't about who your with but how you feel

For me... Growing up, I was always a loner.
But when my ex-wife came into my life, it changed me.
I allowed myself to let another human being to get close enough to get to know me.
When we divorced, the first year was a nightmare. All of those things that I got use too were suddenly out the door. No one to come home to. No one there, to sneak bites from my food. (She did that a lot whenever we would order delivery. She wouldn't dare to order outside of her comfort zone. But she would take bites out of my food just to try it. I didn't mind. Hell, I thought it was funny and cute)
All of the privileges of being married were gone, so it messed with me pretty bad. But then my loner nature took over again and got me through the following years. And at one point. Both versions of myself were integrated.

Aside from 2 brief marriages between '76 and '80 then a long distance relationship on '89 which came close, I've been single. At that point I concluded that my skill at finding(?) partners was as poor as my father's had been and I would be better off single. It is to my benefit that I am an introverted personality type so I actually enjoy a significant amount of solitude. If I were a more gregarious sort, I'm sure I would struggle more with the lifestyle.
I do have friends and when I feel the need for face to face human contact I will go visiting but it isn't a driving force on a daily basis. I do help my 94 year neighbor, take her to senior exercise, library and shopping, take her food when I cook a meal. That gives me a sense of usefulness in the human realm I guess. I do dog rescue so I have regular contact with something live and responsive. Those things help ward off that sense of loneliness and lack of "purpose" (for want of a better term) that is easy to fall into when living alone.
If you have a chance, fit some "pro-social behavior" into your day on a regular basis. You probably do some of it already but make it a habit. Altruistic acts not only help others and society but ourselves as well. "Altruism activates reward centers in the brain. Neurobiologists have found that when engaged in an altruistic act, the pleasure centers of the brain become active." (for more on this: [verywell.com] ) So, when you "pay it forward", giving some of your time, energy and talent to help the world, you will give yourself some kindness as well.
If you have a special skill/talent, share it with others. I carve and for years I taught classes on carving, not for pay but it was really rewarding to me as well as sharing that art form with others. Even if it is just something like taking a friend/neighbor/relative who also lives alone, out to dinner occasionally, you will be surprised how it can raise your spirits. Make it a "routine", meeting that friend on a weekly basis to eat out together or go to a movie or shoot pool.
Although it is unlikely to keep the lonelies away all the time, doing these kinds of things could have a big impact on day to day feelings of loneliness or like something is missing from your life.

"What wisdom can you find that is greater than kindness?" -Rousseau

Its no fun cooking an eating by yourself, Its no fun going out to eat or to the movies by yourself. Its no fun taking a road trip or vacation by yourself. Its no fun going to the beach or hiking or having a few drinks on the back deck on a nice summer day by yourself. But I do it. I just go through the motions.

I have hobbies and enthusiasms that keep me occupied in life. I think I could potentially be single forever and still be okay because there's plenty to be excited about in life. I always have some battle in life I'm engaged in, some hill I'm climbing that keeps my attention. Maybe eventually I'll find someone else on the same hill

I am lucky to have my daughter with me. It helps with the loneliness. I still do miss having someone around. Especially in the evenings. I have friends that I talk to. I try and keep busy with projects. It is not easy and I hope to find someone to share my life with but I'm trying not to force it.

Alcohol...

...is not the right answer hiccup

Life is busy, I miss having someone, but not really lonely. Only lived with a lady for 11 months in past 24 years and that was in 2004. Other short term relationships were distance.