This question made me think a lot before answering, there aren't that many songs that has special meaning for me. I wanted it to be something optimistic but I just think about the meaning... So it really might be "The Show Must Go On" by Queen. This "Moulin Rouge" video is simply impressive and movie version of the song ❤️
link
I know that the real meaning of that song is a bit different, but,
The meaning for me is: No matter what, show must go on. No matter what you have went through and are going through now. Like Julia Lambert ("Theater" by W. Somerset Maugham and it's movie adaptions) said, life is a theater, it's a show and you have to always be the leading lady in your own life. Often people see just a smiling face, they doesn't know what is hidden inside, maybe there is breaking heart, pain. These are different things that I am learning and have experienced. I am the leading actress in my own show/play and what I am working with the most is the art of acting, to play a role of myself, to not to hide anything anymore. The new chapter is opened leaving everything I want to leave, behind and my show is going on ❤️