When you've got what you consider to be a good thing, or have learned a new process, or have just seen a great movie, don't you just naturally want to share it? I think that's human nature.
What has happened to us as people that when someone approaches us with a very enthusiastic idea or feature or benefit or product or service or movie, we immediately turn skeptical? And some of us have heard about "the next best thing" so many times, we've even gotten cynical. Skeptical: cautious yet still open. Cynical: righteous, judgmental and closed.
So what do we do to alter this situation in which many of us find ourselves, either as the giver or the receiver of this enthusiasm? Let's take it from the point of view of the giver first. So you're excited and you want to share whatever you're learning or understanding. Be really aware of the energy you are giving off. Most likely it's very dynamic, or "push" energy if you're uber-excited. This automatically creates resistence, even without meaning to, because we as humans have been conditioned to be protective of our personal space. When someone pushes something on us, without even thinking about it, we push back or resist. As the deliverer of exciting news, be aware of when you are pushing someone into that defensive state. It's not their fault - they just don't know what they don't know.
As the receiver of uber-enthusiasm, notice your defenses. What is the other person's excitement triggering for you? It's most likely something from your past which isn't even a factor in the current situation. Was it an overbearing vacuum cleaner salesman (or in my case, a steak knife salesman)? Was it the popular crowd in junior high? Was it someone at your church? Just notice. What causes you to put up that wall preventing you from being open-minded enough to listen objectively? Remember: you are in 100% control of the outcome of this person's enthusiasm. You don't have to buy what they're selling, even if it's a new movie they're in love with. Sometimes those people (and put yourself into that position when you've been "those people") just want to be heard and just want to share their insights. You can provide open listening space to allow them to work out their own ideas if you stay out of judgment and in curiosity.
Passion can't be faked and sometimes true passion for an idea or a cause or a team can be overwhelming. The reaction you have to the receiving of that passion is really a lesson for you. Anything that frustrates or upsets you provides a huge message for you. Embrace it and learn from it. And if you're missing passion and purpose in your own life, that could be a reason you're turned off when someone else has found something that's important to him. Again, notice that and remember you're in charge of your emotions.
Can you be TOO enthusiastic? Stay in curiosity and answer that question for yourself.