I came across this phrase last week, and could instantly apply it to my life and the life of others around me. It means literally 'when in doubt, abstain'. This can be a motto for so many aspects of our lives, where the obvious choice is so rife with uncertainty, we need a glimmer of guidance, maybe a glowing path - or maybe a rainbow road- to see us through.
As a friend of mine -who is in the dating world - said to me, "doubt is always a factor in the dating stage of any relationship". I in turn told him that indeed there is always doubt, but there are many kinds of doubt. Doubt that a potential partner will be faithful is much different than the doubt that he/she is as good a cook as he/she says he/she is. The latter is trivial to the pondering doubt that will forever linger in the back of the mind of the 'partner of little faith' until it eventually wears the relationship thin. These types of doubts are the ones that could/should cause us to abstain.
In trivial moments with trivial outcomes we could probably say, 'when in doubt, flip a coin', but in matters of heart, home and health.. I think, when in doubt, abstain.