Working on a different jam right now, so my submission's going to take a hot minute. I'm going to post above mod so it can freely be borrowed.
Roll 1d6 when attempting something difficult:
Roll < Stress: Success with minor consequences, generally +1 Stress. May roll an additional 1d6, and add to Roll.
Roll == Stress: Success with minor consequences, +1 Stress.
Stress < Roll < 7: Unmitigated Success.
7 <= Roll: Failure, major consequences, possibly even death.
When stress == 7, reset stress to 2, suffer major consequence.
If you have an applicable trait or bit of kit, you may roll two dice, and take whichever you prefer, *before* rolling additional dice if Roll < Stress.