Everything in my power
“I will do everything within my power to …”
Stop right there. Unless you mean it. And if you do, then by all means (as you’ve suggested) do everything you can.
But be careful about making promises to “do everything in your power” unless you’re planning to do just that.
Because as we all know: in many ways you are extremely powerful (whether you like to admit it or not).
“Everything in your power” is a huge promise.
But of course, for some things, it’s a promise worth making.