"To understand me, you have to meet me and be around me. And then only if I'm in a good mood - don't meet me in a bad mood"

In this quote, Avril Lavigne is expressing that in order to really comprehend her, one must spend time with her and be in her existence. Nevertheless, she also includes the caveat that it need to be when she is in an excellent state of mind. This recommends that her mood considerably affects her habits and how she presents herself to others. It also indicates that she might have a tendency to be moody or unpredictable. By specifying not to fulfill her in a bad state of mind, she is setting borders and stressing the importance of positive energy in her interactions with others.