I'm in my third marriage with 14 years under our belts, I have one son who is married and has two sons of his own, so far. My wife has a son and daughter just older than my son. Hers are both single in their mid-30s.
I, too, get depressed sometimes. Some depression comes from the weather. In the Winters, I am more likely to be depressed from that.
Besides that, though, some days I just have to talk myself into going somewhere and doing something. I might think of something to do, mull it over for a while, and reject it. Other times, I think about an idea, realize that it's a good idea, and start putting one foot in front of the other until I'm engaged in that activity. Yes, sometimes, it's that first step with the activity in mind to get me to do something.
I don't suggest church. I'm atheist, so I don't have to attend the meetings, and I cannot suggest it for anybody else, just like Ghandi couldn't tell a child to quit eating sugar when he, himself, ate sugar. He had to rid himself of that for 3 days, according to the story, before he could advise the child not to eat sugar.
So, where does that leave us? Do you have a senior center near you? Our county supports several centers, which are all free; although, some of the activities do cost a little bit depending on the center. Usually the costs are for materials or maybe certain equipment you might need, such as wood for wood carving, clay for the pottery classes, or yoga mats for the yoga classes.
I have two centers within 3 miles of my house. I tried the one in my town, which was the farther of the two, since I live near the South end of my town. Even after a few visits and after meeting several other attendees, I couldn't seem to click with anybody. Then, I tried the closer one, which is in the next town, but unless one notices the "Welcome to" signs, one cannot usually distinguish where one town ends and the other begins.
After just one visit or two, things started clicking at the closer one and I've been going there fairly regularly for 4 or 5 years now. If you try this, I'd suggest allowing yourself at least three visits, unless the experience is too stressful for you or the idea too repugnant in the first place. The three visits might give you enough insight on how things work there to make an informed decision about whether or not to continue.
Sometimes I go to play Euchre on Tuesday and Thursday mornings. I was there this morning, but was informed when I got there that the others had called it off for today. So, I went into the cafeteria and visited with some of my friends who were in there.
Sometimes, I use the work-out facilities in their small exercise room. I've played pool, Texas Hold 'Em, and Mexican Train dominoes at various times. I've eaten lunch there. I've also avoided yoga classes, zumba classes, and many other activities that I don't enjoy. I've thought about the pottery classes and even wood carving, but I haven't done those, either. I guess I'm not ready for the commitment to be there at the times those classes are offered or when a dried pot needs to be smoothed and painted for firing.
One of the guys who plays Euchre goes to both of the centers I've mentioned.
Another thing you might do is consider joining a recreation center if you haven't already. I buy an annual membership at our town's public center for $135 a year. They have an inside walking and jogging track, basketball and pickle ball courts inside, a weight room with machines and free weights, and a good sized indoor pool, with water aerobics classes or swimming on one's own.
If you get involved in activities where others are involved, I believe you will have little trouble finding acquaintanceships, friendships, and maybe more. I can guarantee that it won't happen if you don't meet anybody, somewhere.
One key might be to act on thoughts you have about things you can do. Once you think of something - taking a walk, going swimming, or whatever - then put one foot in front of the other until you find yourself heading there to do just that. Even in my deepest depression, I can sometimes put one foot in front of the other toward something, even if it's just walking to a nearby park and going around it a couple times.
Good luck in your search for the next great adventure - or little one, who knows?