。
Even if you fail, don't get discouraged.
Literal
By-chance fail-even-[concessive-ても] give-up don't-[prohibitive-な].
くじける ('to get dispirited, to be crushed') carries a physical, visceral image of bending or collapsing under pressure — bones, plans, and spirits all くじける. Combined with the bare prohibitive ~な, the line lands as blunt, masculine encouragement: 'don't let setbacks crush you.'