My players sometimes groan in anguish as I keep rolling between 15 and 20 and they roll between 1 and 4 on a d20. And when they fail their Fort save against the phase spider it does 15 Con damage (2d8)... So these days I try to talk a lot more to my players: What's their fall-back option? How will they react when the parley goes bad? How will they escape when they fail their rolls? I want them to have backup plans available that will work even if they fail a few critical rolls. I also try to spread monsters over time: I know there are 50 Lotus Eaters in the camp, but once alarmed they party can fight on the retreat and I'll find an in-game reason why the reinforcements are too weak for the TPK they have in mind.
As for the dice, I started to play it up as an additional source of entertainment: No, no, you take the ugly dice. Yeah, those! I have my green DM dice right here. Don't touch them!! You're infecting my dice with your dismal luck! What do you expect with pink dice? You deserved it! That leads to a lot of teeth wear but also in some roaring triumph when the archer finally does take down that efreeti or that green dragon with a critical hit.