Too much of a good thing is a bad thing. In the case of introverts, alone time is a good thing. They need it to recharge. Too much alone time, though, is a very, very bad thing.
solitude
Loneliness is not Solitude
Therefore, my dear friend, I know of no other advice than this: Go within and scale the depths of your being from which your very life springs forth…For the creative artist must be a world of his own and must find everything within himself and in nature, to which he has betrothed himself.
– “The First Letter,” Rainer Maria Rilke