One of the joys of poetry is being able to find your own personal interpretation regarding the meaning of the poem. "Stopping by Woods on a Snowy Evening" is a prime example of this. Poet Robert Frost has provided a text that could be referring to the approach of the death of the speaker in the poem, or could be reflecting the commitments weighing upon the speaker.
Winter, the time of year in which the poem is set, is frequently used as a symbol of death, as are the ideas of cold and dark. Sleep is often compared with death. So, when the poem refers to "the darkest evening of the year" and "before I sleep", those could be references to approaching death.
However, the speaker is out and active on that short, dark, snowy evening, with "promises to keep and miles to go before I sleep". The speaker may simply be taking a few minutes to enjoy the quiet tranquility of the "lovely" woods before continuing with a busy schedule that will keep him/her active long past bedtime.
You need to determine what you feel is the actual meaning.