I've done quite a lot of martial arts and fought quite a bit. I don't like it, but I wanted to learn about it. There is something important to understand about fighting (which I assume you already know): hardly anybody wins a fight without getting hit at least once. Fighting is as much about getting hit as it is about hitting. So if you want to fight, you either need to want to hit someone so badly that you don't care about being hit, or you need to be the kind of person who kind of likes being hit.
Most aggressive people I know are aggressive because it suits them. They have very high stress tolerances. If you get in a conversation with them, they will simply turn up the stress levels until everybody else drops out. Then they win. Sun Tsu said, never stand on dying ground. What that means is that if you are losing hit points faster than your opponent, all they have to do is to stand there until you die. You have already lost.
Asking your boxing instructor for advice is not necessarily the best place to go. Every person has strengths and weaknesses. A boxer needs to be able to stand in a place where they can't run away. Then they fight another person. The only way to win is to make sure that the other person is losing hit points faster than you are. You must be aggressive.
A ninja, on the other hand will simply hide outside your window until you are asleep and then kill you with a poison blow dart (totally made that up, BTW -- I don't think ninjas actually did that, but you get the point). If it doesn't look like it will work out, they will run away and kill you another way. Aggression is not necessary.
People who are successful with aggressive strategies will usually advise aggressive strategies. Boxers and other sports oriented martial arts practitioners intentionally choose a system of engagement that enforces their preferred strategies. I always loved listening to people talking about martial arts and saying, "Well, in a real fight, that wouldn't work. Your martial art is so crap." I'd always be thinking, "Well in a real fight, I'd be running away so fast that you'd never, ever catch me". I mean, I'm a very fast runner (true fact: For my black belt exam they sent 20 people after me to help me understand that you can't win every fight. I ran away. Apparently I was the first person to try that approach).
I'm going to hazard a guess that you actually don't have a problem with aggression. You have a problem with winning. Similar to aggression, there are people who will simply turn up the heat until they bake everyone else out. You say that you don't work in a horrible politics-only corporation. This says to me that you don't like dealing with people stealthily stabbing each other in the back to get what they want. If you start playing the politics game, there will be someone who will think, "Yay! Another play partner for me to crush". And they will make your life a living hell -- because they can either generate that hell at an incredible rate, or they can tolerate any hell that you can throw back at them (and may even enjoy it).
No matter what strategy you pick to win, there will be someone who loves that strategy and who is willing to go just that little bit farther than you are. They are willing to put up with just that little bit more than you are. Just so they can win.
Imagine that there are 6 people. A guest comes by and drops off 5 cupcakes. Oh! Not enough. One person may think, "I won't have one. Then there will be enough". Another person may think, "I'd better rush to get a cupcake or else I won't get one". And yet another one will simply walk up and take all 5 cupcakes. "Each of us had an equal chance to get all five of these cupcakes. You guys were just too slow. This is the only fair method of distribution", they will say as they devour all of the cupcakes.
It is not aggression that wins the cupcakes. It's being a jerk. It's being willing to go just that little bit further. It's being willing to tolerate the stares and arguments. It's being able to confidently reply to any complaint, "Well, you are just mad because you are a loser".
And you know what... I think that choosing not to play this game is a completely sane choice. There are consequences, for sure. However, it is worth considering that you might actually prefer those consequences.