Mairg téid a tacaib in chraind.

Mairg téid a tacaib in chraind.

(woe betide * (who) goes * from * rungs * of the * pole)

Woe to the one who slips from the rungs of the ladder.

The reference here is to the "ladder" leading to heaven. In English we sometimes use the image of falling off "the straight and narrow" to convey the same idea. The saying is collected in ACL and quoted in DIL s.v. "taca".