The hardest decision to make is to abandon a cert ride or deciding to cut off part of your route during a rally. I usually build in an "out" where I will identify a bonus or group of bonuses to drop and the time savings should I need them. In 2019 I dropped two that combined were almost 20% of my total points and that was a very difficult decision, however had I not done so I likely would not have finished. That was due to a mistake I made 4 days earlier which cost me 4 hours.
If interested, check out the links to my other rides and rallies on my blog. This was my 4th IBR and the other three are written up as well. If you read the rally report for 2017 you will see why I knew better than to forgo adequate pre-rally inspection/maintenance