This scene from Doctor who I seen when I was a kid. It was the second episode and the Doctor took his companion (Rose Tyler) to see the end of the earth in the far future. Rose ask the doctor if he going to save the day but he tells her no. She ask him why and his answer is "Everything have it time and everything dies."
That quote is something that I'll never forget as It probably the first time I ever realize that I am going to die one day which was eye opening to say the least. It taught me that I should use my time having fun and doing stuff that I genuinely enjoy as well as living my life the fullest.