A lot of people make themselves miserable because they think there is only one way of doing things or one way to look at the world. They refuse to deviate from a certain thought or behavior and then wonder why they're stuck or have limited options.
The key to being happy in life is to embrace ambiguity because not everything is black or white; right or wrong; good or bad. There are a lot of shades of grey and nuanced ways of looking at the world. Be open to all the opportunities available to you and all the wonderful thoughts and ideas that can help you be the best you possible.