Social support is important in the prevention and treatment of many mental health problems. Almost always, people with strong social networks are less likely to develop a mental health problem. If they have a mental health problem, they are more likely to recover than people with less robust social networks. A strong connection with others is not a guarantee of mental health but is a great preventive factor and an effective way to overcome problems.

The size of the social network is not as important as the quality. A person with only a few close friends may feel very connected.
Social connections can have their effect on mental health through different mechanisms, including:
- Preventing loneliness
- Assisting in problem-solving
- Sharing burdens
- Encouraging physical activity
- Encouraging sensible behavior e.g., less smoking or less drinking, safer driving
- Making us feel wanted or loved

Some social connections can be negative. My father was always urging me "Not to run with the wrong crowd." People who spend time with people who are hostile or negative to them are unlikely to benefit.
You can increase your social connections with friends. It takes time. Don't get discouraged. There will be many false starts.
But you can do it.
Go where people are

If you don't go where people are, you won't meet them. Join a group that you are interested in. You may
If you don't go where people are, you won't meet them. Join a group that you are interested in. You may have to step outside your comfort zone. Try it. You might: go to a church; join a club; or take an in-person course, take a fitness or swimming class; or volunteer at some charity.
Make small gestures
Trust that most people will respond positively to you. Reach out, in small ways to more people. Smile and say hello to people you meet. Start conversations when you have the opportunity. Many of these conversations will not go anywhere. They will build your social skills and make you and the other person feel better. Some will develop into friendships.
Heal broken relationships
Reach out to people who are missing in your life, either because of a previous disagreement or because of drifting apart. Let them know they are still in your thoughts. Maybe it is time to restart the relationship.
Choose forgiveness over spite. Spite is not good for you. It can trigger a low mood or depression. Consider the big picture in arguments. Do you value the relationship? If so, why give it up because of a problem?
Apologize for your part in what happened. Almost always blame for a problem is not all on one side. Define the offense, take responsibility, and express regret.
For example, if you found out that a friend gossiped about you, and you had an angry exchange and you haven't talked for months. You might say "I got very upset and didn't listen to your explanation. I should not have done that. I am sorry." You would be taking responsibility for the part of the argument that was your responsibility. They may or may not apologize for their part. Mutual apologies are better but not necessary. You can forgive someone, even if they have not apologized.
Ask for help
Ask for help when needed. Most of us are pleased to give help (if it is not excessive), but we are afraid to ask for help. Asking for help can strengthen social bonds because it makes the other person feel good. It also gives you a chance to get to know each other. Ask for minor assistance. You might ask a neighbor for help. "I will be away for 3 days. If you notice a parcel at my door, could you keep it until I return."
Give emotional support
Give emotional support to those in need without imposing it. Validate their feelings. For example, an acquaintance tells you they are preoccupied because they are going to a funeral. You might say "It must be hard. Do you want to tell me about your friend who passed?" Insisting on giving emotional support when it isn't wanted will drive people away.
Praise others
Be alert to chances to praise others. Praise people honestly, specifically, and generously e.g. "I really like the way you put up your Christmas lights. They sure caught my eye. They are beautiful." Praising others can make them feel good. It can also make you feel good.
Connecting with others is a process that takes time and effort. Different approaches are helpful.