As you experience things in life, you learn and change because of them. This happens to the best book characters, too. Great books have character development...but there’s no rule that your character always has to improve as a person. Sometimes, characters end up growing backwards before they can start moving forward.
Lessons Learned
As an author, it’s your job to put your characters through awful situations. Give them what they want and take it away. Make them fall and hurt themselves at the wrong time. Reveal a terrible betrayal. Some characters take in all this badness and become better people because of it. But, some don’t. People don’t always improve through life. Some of them pick up more flaws as they go along. This is what I like to call growing backwards. It can be a lot of fun to write, if you can make your readers hang around to read it.