Some people here have great ideas, but I also think this is a state of mind. I have been very solitary for most of my life but never actually felt <em>lonely</em>. I knew I always could connect with some people out there who were friends or family, but most of my time was spent alone because I preferred it that way.

There are always people nearby, whether they are in the physical world or online. It's difficult to really be <em>alone </em>when you can always reach out to people with today's technology.

I realized that the difference was within myself when I began to enjoy doing things, whether people wanted to join me or not. Going to movies -- alone. Going out for dinner -- alone. Going to a nightclub -- alone. Some people are terrified to do these things by themselves! I did all of these things and more, and found that many people approached me with ease because I wasn't in an intimidating group with friends. It opened me up to allow someone new to come over to me and say, "Why are you alone?" We'd have a conversation and I'd either make a new friend or have a pleasant experience talking with a stranger.

The more I did this, the more comfortable I felt about being alone. You have people around you, as we all do, but do you also like your company well enough? When you are comfortable with <em>you</em>, the rest falls into place without you even realizing it.

Having this sort of comfort allowed me to meet my husband years later. I married late in life. My attitude was that I would rather wait and have it be the right time with the right person, than rush into it because I was lonely and impatient.

Join a team sport. There are all kinds of skill levels and all kinds of teams out there.

Volunteer. Dog walker for the local animal shelter? Bicycle mechanic at the youth center? I looked at my local Volunteers Needed website and there are about 80 organisations that need help.

Take a class. I took a film making class once. Two nights a week for eight weeks. It was great.

Exercise socially. There are running clubs, biking clubs, hiking clubs.

What are your interests? Identify what interests you and become a joiner. There are astronomy clubs, book reading groups, photography groups. There are LARP groups, choirs, rock bands, dance groups. Do you like art? Take an art class. Stars? Join an astronomy group. etc.

Every day, try to help one person.

Your loneliness will fade.

As @Ian said, try and help one person a day, even if you just smile at a stranger. As you have felt like this for a while, you might be suffering from depression and consider perhaps talking to someone about that. There are free groups online to help manage depression, anxiety etc. which you can explore if you don't want to talk to a therapist.

I hope the feeling fades soon. Loneliness is a terrible thing.

At the end of the day... We are all alone.