苦头

suffering
这是我们吃了～总结出来的经验。These are lessons drawn from our setbacks in the past./听不进群众的意见，早晚要吃～的。If you turn a deaf ear to the masses’criticism,sooner or later you’ll have to pay for it./吃～suffer setbacks; suffer/吃尽～endure untold sufferings; suffer enough from