grin and bear it意为“逆来顺受，默默承受”。

【例句】
I don’t want to spend the whole weekend working, but I guess I’ll just have to grin and bear it. 
我不想整个周末都工作，但我想我也只能默默承受了。

You have to grin and bear it when you have to tolerate an unpleasant situation because you have no choice.
我的工作毫无前途，但是我目前还是得苦笑着忍受下去。