Why should I let the toad work Squat on my life? Can't I use my wit as a pitchfork and drive the brute off? (1-4)
The description of this metaphorical toad squatting on the speaker's life feels pretty oppressive. The verb "squat" heightens the feeling—it somehow seems more aggressive, rudder, and more permanent than, for example, "sit." And we can certainly tell the speaker doesn't want the toad there; he wants to "drive the brute off" with a "pitchfork." He definitely wants to be free of that toad.
Six days of the week it soils […] Just for paying a few bills! That's out of proportion. (5, 7-8)
The speaker feels stuck. He's working all the time just to get by. You know that saying about all work and no play making Jack a dull boy? Well, that's the life our speaker is living, and he doesn't like it. The lack of balance has left the speaker feeling stuck in a life where the only thing on the horizon is more work. That can make it pretty tough to get out of bed in the morning.
For something sufficiently toad-like Squats in me, too; Its hunkers are heavy as hard luck, And cold as snow. (25-28)
Bad news. The sense of confinement and lack of freedom that our speaker feels isn't just the result of being overworked. There's an internal cause as well. Not only is work squatting on his life and holding him down, there's something that "squats in [him], too," and it's just as unpleasant as that brute from stanza one. This internal toad comes with lots of suffocating weight ("its hunkers are heavy") and imagery (like the cold confinement of being stuck in a snow drift). Looks like there's no getting free of these toads. They're everywhere. We might recommend a good exterminator.