The solitude is just a state, but loneliness is an emotional response !
So, the meaning is not exactly the same. Maybe the solitude is useful sometimes. Unlike loneliness, that's not a healthy emotion. That's why successful people are not lonely, but they could work alone. Maybe because they already tried to do something for a company or an organization, and they decided to do it their own way. Maybe that's why successful people, don't have so many real friends. They could have a few, one or non. They understand that the solitude could be better for them. So, less destruction will be, and more focus on success.
But sometimes the total opposite happen. People may get tired, stressed or depressed. They may decide that the solitude may help them. They may think that cutting all the connection is the solution. They may start to do almost everything alone, and that solitude may turn to loneliness. In this situation, they have to change immediately. They have to understand that the solitude is not the loneliness. Alone doesn't mean lonely. We may work on something alone, but we shouldn't forget to satisfy our needs of communication. We should be social, and we should find ways to that.
We always do our best to change for the best. That's why we have to always improve our communication skills. The more we got in touch with people, the more we learn from them. Life is about always finding something new to explore. Life is improving all the time. Maybe that's the beauty of the imperfection. That what make us always try to be close to perfect. That's what push us to do the good for ourselves and others.
Even if we are tired, taking some rest from everyone. We should come back to interacting with others again !