Your growing opportunity is missed if mistakes are not strictly analyzed
You will miss the chance to grow if mistakes are not strictly analyzed
A chance to develop is missed if you do not look at your mistakes as mistakes
ミスかどうか、自分に厳しく判定しないと成長の機会を逃すよ は様々な言い方がありますが
-Your growing opportunity is missed if mistakes are not strictly analyzed
-You will miss the chance to grow if mistakes are not strictly analyzed
-A chance to develop is missed if you do not look at your mistakes as mistakes
この３つを挙げてみましたが、個人的には３つ目が良いと思います。
A chance to develop is missed if you do not look at your mistakes as mistakes
この他の言い方は
Your chance for growth is missed if you do not look at your mistakes as mistakes
Your opportunity for growth is missed if you fail to look at your mistakes as mistakes
Your chance to mature is missed if you fail to recognize your mistakes
ご利用いただいきありがとうございます。
またの質問をお待ちしております！
You'd better judge yourself strictly when you make a mistake so that you can improve yourself.
‘ミスをした時は、自分自身を厳しい目で判断したほうが良いよ、そうすることで自分自身の事を学べるよ’
had better to~ ~したほうがよい
to judge 判断する
strictly 厳しく、厳格に←strict (形容詞)の副詞系make a mistake ミスをする、間違いをする
to improve 改善する、改良する、上達する
カナダ 
日本 
