I am not aware that we know who in particular is the subject of this excellent and famous poem by Robert Frost. However, I think that if we look at it we can find lots of links between it and the general characeristics of Frost's work that will help us to understand it.
It is obvious that this is a love poem. Interestingly, Frost at first gave it the title "In Praise of Your Poise," and it was featured in his collection of poems A Witness Tree. Frost received a Pulitzer Prize for this work in 1943. Although it is obviously a poem of love written in the sonnet form, after the style of Shakespeare, yet it is clearly a lot more than this.
We can see this poem as being a metaphor concerning not only love, but also poetry and life. Note the way in which the tent stands alone in nature, pointing bravely towards the sun during the middle of the day. In the same way, we can argue that the poet faces the challenge of trying to stand firm in the metaphorical field of his art, whilst being pulled in various directions by the many different commitments and distractions that life brings. Some of these distract the poet, making him unbalanced, yet others help him to achieve balance. The poem thus can be said to explore the different conflicts that poets--and all of us--face in life.