Now it’s generally proven that all the negative particles in the speech make a negative and restrict our vision. So, it really seems better to say «I’m sure» instead of «I don't hesitate» or instead «I can't» – just to say what you really can.
The language part of a modern interface is becoming more and more critical and specific. Technical operations are becoming more and more complicated from day to day, but the space for their description permitted on the button space remains the same. And now – attention – just imagine such awful case when this system’s interface should be translated in other language…