The opening verse is set at twilight, or the period between daylight and darkness. The second stanza is written at night, while the last stanza is written in the morning. This is the proper response. There are several other possibilities as well. You could write about each stanza changing throughout the day, for example. Or you could write about the changes occurring within each stanza, such as love growing cold within the first, then being revived by pain within the second, and finally being lost again in death within the third. Whatever direction you choose to take, make sure you mention something from each stage of the day: twilight, night, and dawn. All three stanzas are important, so don't feel like you have to include everything possible within their bounds. As long as there's a clear connection between the different parts of your poem, then it's not necessary (or even desirable) to include every detail. And remember, the more you know about poetry, the more you can do with it. So explore all these ideas and more, and soon you'll be writing some wonderful poems of your own.