Two short sentences carry a surprising turn here. The speaker begins in a familiar place: heartbreak so total that they thought they would die without the other person, who is "the only thing I want in life." It sounds like classic, all-consuming longing.
Then the second sentence changes direction. The speaker says they never wanted to be with themselves more than ever. It's a slightly tangled line, and that's part of its charm. Read one way, it suggests that losing the other person has pushed the speaker toward their own company, perhaps even a first real sense of self. Read another way, it could mean the speaker is still struggling to be alone and wants to escape themselves. The poem doesn't settle which.
The mood is quiet, honest, and a little bittersweet. There's pain in it, but also a hint of surprise, as if the speaker is noticing something unexpected about themselves while still admitting how much they miss the other person.