Being alone and being lonely are two different things.
Not feeling lonely means that you have balance in your life. Being alone and having friends is not lonely. You still have a sense of belonging. You feel that someone cares and you feel wanted or loved. That makes being alone tolerable. You still feel connected even when you are alone.
What is being lonely? Feeling left out. Feeling disconnected form others . Feeling sad because your alone. Feeling uncomfortable being by yourself. The feeling that there is no one in your life who really cares about you. Feeling like you don't have anyone who wants to be with you. Being without friends. Being without a companion. Feeling abandoned. Being unable to connect with someone emotionally or physically. Being in a crowd of people at a party or anywhere else and still having these feelings. Even talking with one person but not feeling connected.
Feeling lonely really hurts but it is normal. When a person has no sense of belonging anywhere in the world and feels trapped inside their own cocoon of life it hurts. It makes the mind hurt which then affects the entire body and it begins to hurt.
There are probably some serious chemical imbalances of the brain and body that can cause someone to feel lonely. So some should see a doctor and have a good checkup. Tell the doctor about the feelings and have him check.
But all to often I meet lonely people who were like me. People who have something hidden deep inside their minds that needs dealt with. For me it was just some really deep thought and dealing with each and every thought and memory that came up. That took a long time and was a very lonely period. I couldn't allow others into my life to distract my thoughts while I dealt with everything that I had locked away in my mind for many years before.
Many people would need professional help doing that. And they should find that! Feeling lonely is not a life sentence. You can get past it with lots of hard thinking and dealing. A pro can help guide you in that and a whole lot faster than you will by yourself.
But being alone and saying your lonely. Common... Next time your walking through a store or even down your own street, try talking to people you meet. Quit getting mad because everyone is in your way and approach them with kind words instead. You may be surprised at all the wonderful people you meet. Not all will be nice, but that's life. Many more will be.
After you run into them a time or two you may even find a common bond. That's the beginning of friendship. Same as at work when you talk to coworkers.
I wasted many years myself looking for friends in bars. Out of thousands of people I found one that was a true friend and not just someone to buy beer for. Most forgot who I was the minute I left the bar. Barroom romance is just that also. Minds clouded by booze and bodies desiring touch and sharing with eyes fogged and not able to see clear. Yup, the kind of relationship that should be tossed with the empty bottles. They do happen to work out good, but that's maybe one in a million.
Even a library would be better than a bar. Kids sporting events can be a great place to meet people for those raising children. Maybe even grand parents who go to watch their grand kids play.
So if you alone but not really lonely then put that big smile on your face and go meet some people. They're out there just the same as you and me!