If I may weigh in, I think a big part of GMing is making the losses and failures feel as important as victories. Communicate! It's easy to get into brinksmanship where your players and you try to screw each other over mechanically, and to me killing an NPC - or a PC - that has had much effort put into building his stats and character out of that spiteful spirit is like kicking over a sandcastle. Communicate! Talk to your player about what this failure or defeat could mean for the character. Make it so that failure makes the PC's plan more interesting instead of completely screwing it up. Do not nullify the player's achievements - and make sure you're on the same page as the players on what that means. Communicate! The best damn rules in the world will not save you if you and your players are antagonists. Competitive spirit is fine, but at the end of the day you're all cooperating in telling a story. Communicate!
And then communicate some more.
(That said, I am incredibly liberal with action die refreshes because in my experience it discourages hoarding behavior, and any character options that give extra dice are easier to parse as just giving an edge in sustained engagements where action dice fly left and right. I haven't had a player heavily invested in Chance Feats so far, though.)