A combination of things. Being on the far right edge of the talent curve helps a lot. Being lucky is important -- one bad roll was enough to kill Hiruzen. Defensive jutsu go a long way. Sticking to your strength in mission types and avoiding bad matchups in combat is critical; e.g. Gai should go on combat missions, not social ones. Have a summoning scroll -- it's not a sufficient item and it's maybe not a necessary one, but it really helps.
Game mechanically:
Have a build that denies the enemy as many opportunities to deal damage as possible and allows you to block as many attacks as possible; don't use taijutsu or Melee Weapons because that allows counterattacks, don't use Ranged Weapons because then you can't parry, etc. Be sure you have enough chakra to support boosting and plenty of Substitution. Have an active career (as opposed to lighthousing), use short, focused plans, and choose things that the QMs enjoy writing. (That usually means punching for my updates and socials for
@Velorien's.)