In my opinion, I believe the underlying theme of this season is the varying degrees of mental issues, our insecurities, and subsequently, the reactions. It is easy for us to say that Lawrence was a degenerate who forgot her birthday and deserved to have his woman explore her options; however, we glossed over the extent of which he was suffering. Just because he was on a couch and stressing a job didn't mean that his mindstate was not severely affected by his lack of employment. Many of us know people who are taught to go to school and obtain an education only to discover that the world is not quite as cut and dry once we enter into the realities of the real world. Only when faced with what seemed as inspiration and hope from his visit to the bank teller, did he see value in himself as he slowly crawled out of that state of depression.
Issa's mental issues are different than those of Lawrence in the fact that she, like many women, have an acute desire to achieve the approval of their friends. As a man and a confident one, I could never know the feelings of what it must be like to desire acceptance. Her immaturity is forced in part due to her closeness to Molly and her avoidance of situation at home. Her reaction to the friend that sought counsel was indicative as how many of us in the community are tone deaf to the importance of mental health.
I think Season 2 will show us more about Issa's insecurities and id be willing to bet that a great amount of her insecurities will come from her folks and how she was raised. The pool scene where she and her pals slung insults reminds me of elementary school students and how when they are faced with a challenge from another student, their initial reaction is to hurl insults to feel better about themselves. The celebratory chants by the friends slinging the insults in a childish manner could draw contrast to behavior of adolescents. We saw this exact same (childish) behavior in the final scene where Lawrence purposefully one-ups Issa to hurt her feelings more than she did to him.
I could go further in depth about the other characters insecurities and mental issues but I think we as viewers conclude that our insecurities can force us to literally become head cases and tote a great deal of baggage around throughout life. Instead of seeking counsel for mental issues that nag at us, we often chalk it up to being a part of life. Adults then attempt to work through these issues as if they are part of recent events when often; they are a culmination of a series of events in life that have not been properly addressed.
The couch on the curb is also an important metaphor for the manner in which old problems (mental issues) fester. A new bouch (Daniel) will never quite fit until she is rid of the old couch that is sitting on the curb like their relationship, which should have been trashed quite some time ago.
With that said, can't wait for Season 2.