Solitude and loneliness are two very different things. People often confuse them. Especially French speaking people because they are translated by the same word.
Solitude is something you choose. It elevates you. It allows you to dig into your thoughts. It forces you to get to know who you are.
Loneliness is something that is imposed upon you, by life, by circumstances, by others. It makes you feel you’re not worthy. It oppresses you when you’re in the middle of a familiar crowd. It darken your thoughts and feelings.