I cruise (and travel) solo all the time. Have been doing this for decades.
I'll be taking my first solo
Disney cruise-the Trans Atlantic-in April to celebrate my 65th birthday. If you participate in these forums (and those on other sites like Cruise Critic for non-Disney Line cruises), you'll know folks before you sail. The only times you'll be "alone" are when you're in your cabin and the times you choose to be alone.
The only trouble I ever encountered was when I was not happy with my tablemates at dinner on one cruise, All I had to do was ask the head waiter to change my seating and it was fine. Many cruise lines now offer flexible dining and I'll always sign up for that unless I'm already traveling with friends I've met on previous cruises. It allows you to plan your day better, eat at convenient times, and dine with more people than if you had the same tablemates every night.
Cruising solo is an ideal way to travel as a single. Remember, you're already part of a "community" the minute you set foot on a ship.