This is one of the sayings I hear and it can bug me.
As a Sikh, I do believe in re-incarnation in whatever form it takes until the cycle is broken but I hear this "You only live once" from fellow Sikhs.
Yes, I can understand that in this current life, you have to experience things and you try to live life to it's fullest and in the best way possible.
However, I also understand you have to live in present but people who follow this thinking don't put any thought into the consequences of their actions.
I think it is irresponsible.