I am gone
halak (haw-lak')
to walk (in a great variety of applications, literally and figuratively)
like the shadow
tsel (tsale)
shade, whether literal or figurative -- defence, shade(-ow).
when it declineth
natah (naw-taw')
to stretch or spread out; by implication, to bend away (including moral deflection); used in a great variety of application (out), stretch (forth, out), take (aside), turn (aside, away), wrest, cause to yield.
I am tossed up and down
na`ar (naw-ar')
to tumble about -- shake (off, out, self), overthrow, toss up and down.
as the locust
'arbeh (ar-beh')
a locust (from its rapid increase) -- grasshopper, locust.