A completely different take on this phrase is that discretion means being discrete as in protecting people or information from exposure in some manner. If one is to be perceived as possessing valor by others, then they cannot express this by being merely brash and powerful.
Probiotics are essential (for at least a month or two after the antibiotics stop, depending on the potency) when you have had antibiotics to replenish the beneficial bacteria.
In general, though, probiotics are espoused for a variety of ills, everything from constipation to cancer treatment. Scientists believe that probiotics work by repopulating the gut with good bacteria, which can be eliminated along with bad bacteria during a course of antibiotics.