A "mood" is a vague sense of emotion about something. My mood can be happy or sad or depressed. Somebody who changes emotions unpredictably is said to be "moody". Keeping these points in mind, we can understand what "in the mood" means and how it should be used. "I'm in the mood to eat" means that you're mildly (vaguely) hungry, or what we might call "peckish". We could contrast this with the words "hungry, starving, ravenous" which mean increasing levels of motivation to eat. So, you can say, "I'm in the mood to..." anything, really. As long as you mean that you're only slightly motivated to do that thing. Caveat: If you only say, "I'm in the mood," with nothing else, it means you want sex.

the other way to say that is I am in this state of mind, like I am in the right frame of mind to win in life, or I am in the state of mind to be a better person now

in the mood can also be a sexual euphemism so stick to certain things for in the mood for, such as food, also when you are unhappy I am not in the mood for that