Reining in enthusiasm

I have an issue with reining in my intellectual enthusiasm. This was an issue for me in grad school, and is likely part of why my dissertation proposal was rejected. I get too excited and interested in things and make my projects too huge - too unfocused, and it confuses people (and I get annoyed when people express confusion, because to me it all makes sense).

And I'm running into this again in my new job, and it kind of makes me want to give up because I don't want to have to hear the critical feedback about it.

I'm creating a grant proposal for a program we want to get started. There is the main piece and then a teeny tiny little adjunct piece. That latter really excites me so I put a lot of attention on it in the draft of the proposal letter. But it diffuses things, and it confused the grants people I met with (to get their help in finding grants - gotta say, so far I'm disappointed in their level of help).

When they said that, I got overwhelmed with a sense of incompetence and all those feelings from grad school .... not being focused, questioning my ability, my intelligence, etc.

Do any of you struggle with this? I need to delete a full page from my letter. Maybe I should adopt an adage like choosing accessories - look in the mirror and remove one. Maybe I should remove one idea from the proposal.