Book II, 54: On Mans two enemies

Two potent Enemies attend on Man;
T'one's fat and plump; The other leane and wan;
T'one faunes and smiles; The other weepes as fast;
The first Presumption is; Despaire, the last:
That feeds upon the bounty of full Treasure;
Brings jolly newes of Peace, and lasting pleasure:
This feeds on want, unapt to entertaine
Gods Blessings: Finds them ever in the waine:
Their Maximes disagree; But their Conclusion
Is the selfe same: Both jump in Mans Confusion:
Lord, keepe me from the first, or else, I shall
Sore up and melt my waxen wings, and fall:
Lord, keepe the second from me; lest I, then,
Sinke downe so low, I never rise agen:
Teach me to know my selfe, and what I am,
And my Presumption will be turn'd to shame:
Give me true Faith, to know thy dying Son,
What Ground has then Despaire to worke upon?
T'avoid my shipwrack upon either Shelfe,
O, teach me, Lord, to know my God; my selfe.