There's more to it. When you say: No, because ..., you are pointing out SOME of the dependencies that must be resolved before you can get to the final goal. When you say: Yes, if ..., you are enumerating ALL of the dependencies, that when overcome, you can achieve the final goals. In addition to the negative/positive connotations, the former implies that you might have stopped thinking about the problems half way, whereas the latter shows that you've thought about ALL the details.

I used to be in the No, because ... camp when I first got out of college, until I met a mentor who led by example with a "Yes, if ..." attitudes, and I am now firmly in the second camp. Usually comprises and trade off needs to be made, but stop thinking about the problem definitely doesn't help.