I cannot disagree more. Opening up my ideas to ridicule and critique has been the best thing I've ever done. I don't waste time on the bad ideas, people get behind the good ones, and people see that I'm always doing something. I don't have to deal with the "what happened to that project you were working on" question much because my standard answer is "Boy was that a good learning experience! I showed it to X, Y, and Z and they gave me great feedback and inspired a bunch of new ideas that are more interesting. Take a look!"
Sure, I don't finish everything, but the important bit is that the things I fail to finish are less good than the things I do finish. This is the "fail fast" mantra in a slightly larger nutshell.
I think there is merit in your argument; having something more tangible than an idea means a lot more, especially when the op sounds like he is quite open with his ideas and willing to express that initial excitement.
Maybe restraining yourself from this might make you work towards having something more substantial that you can then in turn "show off".
Sure, I don't finish everything, but the important bit is that the things I fail to finish are less good than the things I do finish. This is the "fail fast" mantra in a slightly larger nutshell.