You can’t be always be happy.
You can’t always see the truth and the right.
You can’t alway feel great.
Is it that big of a deal? no, I don’t think so. your mood depends on the things that happen in your life. So, it changes frequently. Thus, it is important to know how to deal with it.
What you need to change is getting affected easily by your mood and letting that get to you head. And you have to work on recovering fast from that and not letting it affect your life negatively. And the key for that is to stay focused in your life.