body of water under cloudy sky during daytime

The "always stay in the bright side of life" is not always accurate. Because if you ignore your problems and don't do anything except for deny it exists you are not growing. If you stay happy all the time, all these feelings you hide will eventually overflow and cause worse emotional results. Most of the time the dark side is where you are put into challenge, and if you are able to overcome that challenge you will emerge to the bright side with your mind even more powerful than before.