I was jealous of him because I knew I couldn't do what he did.
I now realize I was envious of him because he is capable of things I am not.
ーI was jealous of him because I knew I couldn't do what he did.
「私は彼がしたことを出来ないと知っていたので、彼を妬んでいたのだ。」
I was jealous of him で「私は彼を妬んでいたのだ」と言えます。
ーI now realize I was envious of him because he is capable of things I am not.
「彼は私が出来ないことができるので、私は彼のことを妬んでいたことにたった今気がついた。」
I was envious of him を使っても「私は彼を妬んでいたのだ」と言えます。
capable で「〜の能力があって・〜が出来て」
ご参考まで!