If a reviewer sees a fishing expedition, your proposal is sunk. Focus your thinking and writing. You Write Get inside the reviewer's head. Make sure your writing reflects this. Some reviewers may not be experts in your area of research, and you are just as obligated to communicate with them as with the leading researchers in your field who know all the techniques and jargon.
Little things mean a lot.
Reviewers don't like surprises - altered format, instructions ignored, information missing or abandoned to the appendix rather than placed in the body of the proposal. The very best scientists fail. Try, try again, but remember that there is a point of diminishing returns. Always be prepared to revise. Take reviewers' criticisms seriously but not slavishly - your ideas and your enthusiasm for them must come through in a revision.