后面的Be in the mood to do sth 是想做某事的意思
例句：
I am not in the mood to really do much writing.
我真没有什么情绪写太多的东西.
而Be in the mood to do sth和 Be in a mood for sth是一个意思的.
例句：
No,really.I'm not in a mood for it.
真的不行,我现在没那个情绪.
但是如果 be in a mood 后面不加For是发脾气,心情不好的意思
例句：
“Dex said you might be in a mood.
“德克斯说你可能闹情绪了.”