It is not for certain that everyone has encountered this. Encouragement is such a lovely thing, but also so dumb. It is as plain as the day, those who have the passion to do will do regardless of opinion, whatever one may say. So do not encourage, do not undermine either, but if it seems futile then tell them so, and if they give up, then they were not meant to be to begin with.
For those that do keep up, if you continue to fail and still continue anyway at the very least know your end point, do not forget that there should be at least a set number you should stand by as a count of failure to success ratio.