The interpretation of this proverb is not obvious, and later writers do not appear to have adopted it from Fergusson.

It is quite clear that sok or sock is the ploughshare.

Seil is happiness, as in Kelly.

"Seil comes not till sorrow be o'er;" and in Aberdeen they say, "Seil o' your face," to express a blessing.

My reading is "the plough and happiness the best lot." The happiest life is the healthy country one.