As a developer I never know if what I say is valid. With the constant changing of technology, a hard and fast rule one day might soon be obsolete. With that in mind, I'm always careful about how much I say I know something. As soon and I say "I'm good at x" there's someone there who can point out something you're not doing correctly, thereby voiding your "goodness".
For me personally this lends itself, to never being too sure of myself in large groups of developers. With diverse backgrounds and training you never know if the idea you offer will be shot down quickly as something you should've known. For example, still to this day I see a lot of people who think the follow is acceptable:
SELECT FirstName, LastName FROM Users WHERE UserID = ' + Request.QueryString["ID"]
(HINT: THINK SQL INJECTION)
If you've been developing that way for years never coming across that vulnerability, you might offer that solution the next time you were faced with a situation where you needed to query. However, if you met a developer who knew better, you're current frame of reference would be quickly shattered when shown how bad the above query is.
Yesterday a developer I really admire and is very popular among the .NET community took an idea I submitted to a newsgroup and commented on it how he liked the idea. Boy that made me feel good. Someone far superior in skill and knowledge was acknowledging a good idea, from me no less. I was smiling for awhile.