Tireless

you have grown used to the tiring, strenuous lifestyle of an adventurer, and do not get exhausted as easily.

Add 1 to you Constitution modifier, to a maximum of 20

For each level of exhaustion you have, you suffer the effects of the level below your current one (level 1 has no effect, while level 2 gives disadvantage on ability checks, etc). This means that you die at 7 levels of exhaustion, rather than 6.