There is a big difference between being lonely and being alone. Often, it is a matter of perspective.
Being lonely can occur while spending time solo or in the company of others. Loneliness is a sad, empty feeling that is sometimes hard to remedy.
Being alone can be life-changing. Much can be gained from time spent solo. New things can be learned. Creativity can flourish. Or, one can just simply be.
We all need to enjoy the company of others from time to time. We also need to take time to spend in the quiet joy of our own company.