It means that someone is going through a very positive time in their life for whatever reason, a time that will always be memorable, and hopefully all of us will be able to look back and remember a time when they were very happy and having an exciting time. If only it could be like this all the time but if we didn't go through bad times too we would have nothing to compare those good times to.
If I could pick out a time in my life where everything was wonderful I think it would be the birth of my daughter. She was born a few days before Christmas and I got out of hospital on Christmas Eve. It was a magical time for me and although some people may not have found it exciting, to me it was the best feeling in the world and I could not have wished for anything better. For others it could be a new romance, new job or maybe a great holiday, but whatever the reason I think we all have times that we treasure and look back on with great fondness,