Is your proposal credible?
Be realistic. Beware of overselling yourself and your field.
For example, even IF you develop the correct theory of cuprate superconductivity it is not a given it is going to lead to levitating trains and a new electrical power distribution network.
The past is a pretty good predictor of the future. The quality and quantity of your output, and the impact of your research, is not likely to change that dramatically, even if you get the funding.
For example, if in the past 5 years you have not done anything particularly significant then it is hard for me to believe you will if you get this grant. On the other hand, if your grants always lead to solid publications that generate interest, then it is a pretty safe bet that another grant will.
Furthermore, if there is some problem that many other smart, technically able, and well funded people in the world are struggling to solve an important problem, it is hard to believe that YOU are going to solve it.