Shelley speaks directly to the future as if it’s a person he adores and longs to find. He asks where this “beloved To-morrow” is, because all of us — young and old, rich and poor — spend our days chasing after its promised happiness. No matter what we’re going through, we imagine that tomorrow holds the comfort or joy missing from right now. The speaker’s tone is tender but quietly heartbroken: he’s caught on to a painful trick. When we finally reach that longed-for moment, it’s already turned into plain old Today, the very thing we were trying to escape. So the chase starts all over again.
There’s a gentle melancholy here, a sense of a wish that can never be caught. The poem doesn’t rage against this cycle; instead it sighs with recognition. The mood is wistful and universal — anyone who has ever thought “I’ll be happy when…” will feel the gentle ache in these lines. Shelley captures how we postpone living for a future that, once it arrives, just becomes another present we’re ready to flee.