When you fail, don't take it personally; it's just a learning experience.

take 在这里是动词，意思是"对待、看待"。 personally 是副词，由形容词 personal（个人的）加上后缀 -ly 构成，意思是"从个人角度、针对个人地"。 take sth personally 这个短语的意思是"把某事当作针对个人的攻击或批评"，即"对...感到被冒犯"。