Quote 52
I felt fear's echo, and along with that I felt the unhinged, uncontrollable joy which had been its accompaniment and opposite face, joy which had broken out sometimes in those days like Northern Lights across black sky (1.5).
A Separate Peace is all about equal but opposite pairs: war and peace, winter and summer, safety and injury, life and death, and here we see joy and fear.
Quote 53
I felt better. Yes, I sensed it like the sweat of relief when nausea passes away; I felt better. We were even after all, even in enmity. The deadly rivalry was on both sides after all (4.34).
That Gene feels better at finding resentment in Finny proves both his jealousy and its source: Finny's character, not his abilities.
Quote 54
Any fear I had ever had of the tree was nothing beside this. It wasn't my neck, but my understanding which was menaced. He had never been jealous of me for a second. Now I knew that there never was and never could have been any rivalry between us. I was not of the same quality as he (4.72).
This is what Gene fears, more than Finny's athleticism or charm – his goodness of heart, his pureness of motive. The question is, then, why is Gene free of fear after Finny falls from the tree? His athleticism has been destroyed, but his character hasn't. What should we make of this?