be spitting in(to) the wind

To be doing something totally pointless, fruitless, or futile; to be wasting one's time doing something that will not or cannot come to pass. To be perfectly honest, when I vote, I feel like I'm spitting in the wind, so I usually don't bother. If you're trying to lose weight without changing your diet, you're spitting into the wind. It looks like I'm spitting into the wind trying to get a raise from my boss.

be spitting in the wind

If someone is spitting in the wind, they are wasting their time by trying to do something which has little or no chance of success. As an approach to the problem, this is scarcely more than spitting in the wind.