What is the ruleset you are sparing under?
MMA type rules where anything goes except for grion strikes, eye gouges and finger locks? Or a more standup type of sparing with just kicks and punches?
Its my opinion that if you are going to learn martial arts you need to learn all the ranges, ground work, clinch work, and striking. I train in aikido, judo, bjj, and muay thai (weird combo I know, but the aikido is done more as a pastime thing, the others are done for competition). I use the muay thai for range with some clinch, the judo for throws and the bjj/judo for ground work (mostly judo, just got into bjj).
If he is training you full contact in all of these ranges then you should learn everything you can. Get a few fights under your belt and open a gym. MMA gyms are charging huge amounts with the success of ultimate fighter on spike tv. I've seen bjj clubs raise rates from judo levels (about 120 bucks for 3 months) to over 85.00 a month (This is in the midwest).
Its really up to you in the end. You dont have to be a violent or agressive person to fight. Fighting is just a skill, it can be used agressivly and passivly. I fight for sport, i'm not the kind of person who wants to fight on the street. I'm not trying to hurt the person I'm fighting and I'm not angry with them. They are just a guy who is competing with me. We are both out there to win, not kill each other. But at the same time, the enviroment could be too hostile to train. I've been a serveral gyms where it was about winning at all costs. The teachers would just wreck you. It was no fun. A good teacher will work with you at the top of your skill level, but not just dominate you.
However, I can't stress enough that good MMA training is hard to find. I dont know if that is what you are getting. If you could describe the sparing and rules a little more I am very interested in hearing what he is teaching. If the ruleset is not formalized, and you can do anything but you have always been doing standup striking, go train some bjj/judo and change the 'rules'. Never fight a man on his own terms, learn to work under your 'rules'. I'm a grappler. I dont like striking. I'm going to try to take you and throw you, then i'm going to try to break your arm/leg/neck or choke you out. When I spar guys from karate or other standup arts they have no idea how to deal with a guy who throws them. They dont know what to do when you throw a choke on. Its even better if they have never spared full contact (like ata tkd guys). I love nothing better then meeting a black belt who has never spared full contact and getting him to spar me. They fall apart the first time they take a solid hit.
Anways, i'm very interested. Give me some more info. I love to hear about how people train martial arts.