Rejoice
samach (saw-makh')
probably to brighten up, i.e. (figuratively) be (causatively, make) blithe or gleesome
not when thine enemy
'oyeb (o-yabe')
hating; an adversary -- enemy, foe.
falleth
naphal (naw-fal')
to fall, in a great variety of applications (intransitive or causative, literal or figurative)
and let not thine heart
leb (labe)
the heart; also used (figuratively) very widely for the feelings, the will and even the intellect
be glad
giyl (gheel)
to spin round (under the influence of any violent emotion), i.e. usually rejoice, or (as cringing) fear -- be glad, joy, be joyful, rejoice.
when he stumbleth
kashal (kaw-shal')
to totter or waver (through weakness of the legs, especially the ankle); by implication, to falter, stumble, faint or fall