The speaker begins in a state of constant fear, and from that anxious place turns inward to look for hope. The word "survey" is the key. It suggests a land surveyor walking a property, measuring and checking its boundaries, only here the land is the speaker's own heart. The task feels careful, almost official, yet the person doing it is frightened.
The last two lines make the picture stranger. The speaker has an acre of land "bought for nothing but a laugh." That could mean the hope was gained cheaply, or on a whim, or that it was never really paid for with anything solid. The poem doesn't say which, and that uncertainty is part of its effect. Is the acre a bargain or a joke?
The mood is quiet, uneasy, and a little wry. Hope appears small and fragile, something the speaker has to hunt for rather than simply feel. Still, there is a faint lightness in the laugh, which keeps the poem from being purely bleak.