Defense wall recovery

Hello,
How can I recover wall life? The only way i find is to spend wood to improve the wall, but the problem is that I lose wall life faster than I can get enough wood...so I think I am missing something

Thanks!

That's the game in a nutshell, no way to win unless you spend money

Dont fear to lose. On a game over, you dont lose sour buildings or characters or ressources. You only "lose" 30 days of the survival counter.

I see, thanks guys!