We respect the uncertainty principle (the Schr"odinger--Robertson uncertainty relation) in describing properly physical phenomena even more in today's or future experiments with opposite results. We explain such a question about the uncertainty principle this: We perform an experiment by simultaneous measurements in order to test the effect of the uncertainty principle. Only commuting observables must be measured thinking in the experimental situation. Thus, the effect of the uncertainty principle cannot be seen by simultaneous measurements.This explanation of the experimental data is our main assertion in this paper. However, what we dare to say is not to disturb the uncertainty principle, but to notice our policy in using the principle, respecting itself. Therefore, we respect the Schr"odinger--Robertson uncertainty relation as the famous mathematical form of the uncertainty principle. We show the Schr"odinger--Robertson uncertainty relation has naturally the understandable upper limit (the Bloch sphere) and the meaningful lower limit (exactly zero). We expect our discussions give some insight for future studies for the uncertainty principle.