Enthusiasm is when people show intense excitement for something, or they have an intense enjoyment of it. Enthusiasm often motivates people to progress their enthusiasms (things they are enthusiastic about) more than they would have if they weren’t enthusiastic about that thing. A good example of this is my Science course. I hate my Science teacher with a burning passion because of this, but he basically poops out random topics for me to learn badly, in the hope that one of them sticks. He just likes to throw random spaghetti at the wall to see what falls and what doesn’t. If I find enthusiasm in one of my topics, the hope is that I’ll run with it and turn it into something useful. This method helped me find one singular topic that I am enthusiastic, at the cost of learning less science than my youngest brother who is taking a newer course in 3rd grade. Basically, it’s a trade-off. I don’t learn anything useful for four years, but during the five lessons that I actually become aware of something that I am enthusiastic for, I get a new hobby and grow my skills in that hobby on my own. All that is to say, I am enthusiastic about 3D printing and I have run with it ever since I first learned about it, but all my other topics that I don’t have enthusiasm for have been a waste of time.
Personally, I don’t think there is such a thing as too much enthusiasm. You just need to exercise prudence in pursuing your enthusiasms. You can’t run in blindly. I don’t think enthusiasm is blinding; I think that if you are being imprudent in pursuing your enthusiasms, it isn’t the fact that you are being enthusiastic, it’s that fact that that you are being imprudent.
In short, enthusiasm is when you are are intensely excited by something, generally something you do, like a hobby. I don’t think you can have too much enthusiasm because you can never be too excited for something. You simply have to exercise prudence when you are enthusiastic about something so that you don’t rush in blind, just like you have to do with anything you do.