Have you ever been told “you’re your own worst enemy”? Or “you make things so hard for yourself”? These phrases hold negative connotations. And normally in our own lives we try to avoid situations where we could be accused like this! Not so, your protagonist.
What better way to make things interesting than to make them an antagonist as well. Looking at their personality traits, flaws and biases can be your starting point. But actually, you may find that you don’t have to go too deep before your character does some dumb stuff that gets them into trouble.
I am currently re-reading the Jack Reacher series, and I can see how Reacher regularly acts against his own interests because of his values. This is what makes things interesting. If he did what his better judgment told him to do, there would be no story.
So I decided to give it a go myself. Already my protagonist had her share of flaws and biases. But she was far too sensible. I decided to make some of her decisions rash. Really rash. Suddenly, she was plunged into a situation she would never normally find herself — outside her comfort zone and in a heck of a lot of danger. Much more interesting.
Avoiding gratuitous bad decision making is also important. So before you proceed, make sure that there is a really good character reason for those bad decisions. Fortunately, with a well formed character (like any human) there are always good reasons to do dumb sh*t. That’s what makes us human, and our characters relatable.