in one's blood 天生就有的、骨子里存在的（能力）

　　I think singing is in my blood.

　　我感觉我天生就会唱歌。

　　Math is so hard for me. It's just not in my blood.

　　数学对我来说太难了，我天生就不是学数学的料。

　　疯狂练习吧！