We take care to choose only G-d-fearing, honest people. These people are keenly aware that G-d is always watching and that they will be accountable for all of their actions, good and bad. When one truly understands this reality, nothing in the world is worth intentionally missing a commitment. Also, because human error is possible, our shliachs each take it upon themselves to start over again if they accidentally miss a day. This has happened in the past, and each time the shliach began another round of 40 days with no extra donation requested. So, either way, you win. In the event of a missed day, we will contact you to let you know when your prayer will in fact be ending.