Two short lines carry a lot of weight here. The speaker begins by apologizing, saying sorry for being "always so sad." That small word "always" suggests the sadness isn't a passing mood but something constant, and the speaker feels it as a burden on other people. Even their pain comes with guilt attached.
Then the second line drops the polite tone: "But who could love me?" It reads like a question the speaker doesn't expect anyone to answer, or one they've already answered in their own head. The apology and the question fit together, since the speaker seems to believe their sadness makes them unlovable.
The mood is quiet, raw, and lonely. There's no description of a place or event, just a blunt confession. The poem's brevity makes it feel like something said under the breath, or a thought that slipped out before the speaker could stop it. It leaves us with the ache of someone who is hurting and is also convinced they don't deserve care.