Twilight is the poem's central image, and it works as a border between two states: the place where dreams stop and reality starts. The speaker points out that the same moment of half-light means different things to different people. For some it is dawn, a signal to wake up and get going. For others it is dusk, when the day is closing down.
The last lines carry the sting. People who slept through dawn, who let the chance to wake up and act pass them by, meet dusk with nothing to show for it. All that is left is to light candles "in Wake," a pun on a funeral vigil and on the waking they missed. The tone is quiet, reflective and a little sorrowful, with a gentle warning underneath. The poem seems to say that dreaming is fine, but if you never rise to meet reality, you end up mourning the life you didn't live, perhaps even your own dreams.