Experience Points
The completion of a mission or quest gets you XP depending on how difficult it was. Once you've accumulated 1,000 XP, you level up, reduce your XP by 1,000, and continue this cycle.
Learning from your Mistakes
During encounters that are life-threatening, you can choose to turn one attack, save, or check you make opposing a dangerous foe or obstacle into one degree less successful than it actually was (critical success --> success --> failure --> critical failure). You get +1 XP per time you do so if the encounter is average difficulty (+2 if Hard, +3 if Very Hard, +4 if Overwhelming, +0 if Easy or easier) to a max of 3 times per scene. You must declare doing this before the GM reveals the results of the failure.