I thought that you would get carried away so I didn't say it, but ~
I didn't say it because I thought you would get carried away, but ~
I didn't say it because I thought you would get carried away, but you're really great!
「調子に乗る」→「To get carried away」
「(私は)と思った」→「(I) thought」
「言う」→「To say」
「言わなかった」→「Did not say」
「君が調子にのると思ったから言わなかったんだけど、~」
「I thought that you would get carried away so I didn't say it, but ~」
「I didn't say it because I thought you would get carried away, but ~」
「これを言うと君が調子に乗ると思ったから今まで言わなかったんだけど、君ってすごいよね」
「I didn't say it because I thought you would get carried away, but you're really great!」