"
All I know at the end of the day
Is you want what you want and you say what you say
And you'll follow your heart even though it'll break
Sometimes
All I know at the end of the day
Is you love who you love, there ain't no other way
If there's something I've learnt from a million mistakes
You're the one that I want at the end of the day
These are life lessons, you must live for the moment and you must seize the day and that you can't always control what is happening like who you fall for, or what you want in life. Since the girl never said "I love you" back to the boy we can assume the part about following your heart even though it will break is about her not loving him back. Again the narrator is saying how even though it was a mistake to fall for he still loves her because he can't help it. And there is not any other way to live. A million mistakes can refer to past relationships that have failed because he did not let instinct take over and love with his heart. Or that he may have cheated on her. And last but not least he is reassuring the girl that she is the one he wants at the end of the day and even though there might be fights he still loves her.