Ok so I realize the title seems confusing, so let me elaborate:
Often times someone with a high level of knowledge in a some subject, may be inadvertently over-charitable to others, in assuming that they too have the same high level of knowledge, and insights that he/she may, whilst more often than not, that is not the case. In doing so, (especially in competitive environments), they may then assume, (and get discouraged further), in initiating a new project/venture with their insights, because they think that "everyone" already knows what they know, and so their idea isn't unique, and may be "already thought-of / done".
Is there a word/phrase that may capture such a thing? It's sort of a cross between selling yourself short because of knowledge/insight, since you falsely believe everyone else already knows what you know.