Solitude does not necessarily mean living apart from others; rather, it means never living apart from one's self. It is not about the absence of other people, it is about being fully present to ourselves, whether or not we are with others.
"Peace is not the absence of war." Spinoza said it, but it is mindlessly quoted out of context, for he added, "It is a virtue, a state of mind, a disposition for benevolence, confidence, justice."