What happens when Pisces Moons get mad?

Pisces moon and mars here. How I deal with a situation I don't like depends on a variety of things; who has made me angry, the importance of the issue, and how my moon was prior to this.
Sometimes I will blow up.. Let it all out and then I am happy. Other times I will blow up and still be annoyed about it but will quietly brood over it. The most worrying times are when I keep it all to myself and stay angry for a while. I will stay quiet, appearing calm to others but inside I'm angry. It's during these times where I feel I have no control over the situation so I don't know what to do. I find it pointless to bring up.. But the thoughts will bother me until I find a way to let them go or bring them up in a way that serves a purpose. Letting go is often the hardest. I will stay angry for ages with someone who has really wronged me and will ignore that person until such a time as I don't care anymore.

I have Pisces Mars and Pisces Moon. I do have Mars square Pluto. @Been There

You have not given us enough information to answer your question.
We need to see the birthchart (the circular map of the sky, done for the date/time/place of birth, done using symbols, numbers and lines).
"Pisces Moon" in insufficient information. That's like giving us a photo of someone's foot and asking us what they look like.

That depends mostly on their Mars. The sign their Mars is in, and MOSTLY the aspects that other planets make to their Mars.

Yes, Moon is involved in anger to some extent. Moon is, after all, the planet of how we automatically respond to situations.
But Mars is the planet of how we feel any desire we have, how we take action to procure what we want, and how we react when we do not get what we want . .or we get what we do NOT want. Anger comes from the frustration of not getting what we want, or of getting what we do not want .. it comes from our "action principle" (which is Mars), since we get angry TO try to make the other person do something different.
Therefore, anger .. as a form of self-assertion and aggression, responding to some desire we have ... comes mostly under Mars.

But yes, there is a some influence from the Moon too. MOSTLY it is determined by whatever aspects other planets make TO Moon.
The sign that Moon is in shows only the general style for Moon .. and all signs have both a positive and a negative side to them. It is the aspect the planets makes that shows whether or not the sign is expressed in a positive way or negative way.

Aspects are specific differences around the circle of the zodiac. Just as music resonates harmoniously or can clash discordantly .. so,, too, different distances have certain "harmonics". So if two planets are a harmonious distance from each other, this means that those two parts of the personality resonate harmiously .. that each inner need paves the way for meeting the other inner need. Obviously with a harmonious Moon aspect, the emotional nature operates smoothly, and the positive side of Pisces will come out. Unless Mars has problems, this person doesn't really get mad very often or very strongly .. they have a lot of compassion and empathy and if they do occasionally get mad they tend to feel guilty and rein it in. DEPENDING ON THEIR MARS.

Other aspect distances create discordancy .. the two needs contradict each other, so when you go to express one need, it interferes with the other need. This creates inner tension, and if either Moon or Mars are involved in this tension, it can indicate a tendency to get angry often and/or strongly. Obviously, this brings out the negative side of the signs that both planets are in.
In the case of Pisces Moon, badly-aspected, there is tremendous guilt ... difficulty getting mad means that they hold it in way too long and it explodes. It means that they have a hard time getting over it, because their guilt makes it difficult for them to face and resolve the issue. But, again, the WAY they get angry will depend on their Mars .. its sign and especially its aspects.