Nick Diaz showed more bizarre behavior over the weekend, missing flights to Toronto and miscommunicating with his new (old) bosses. Cost him a title shot and some serious money. A lot of people have gotten down on Nick and made moral judgements against him. The thing is, Nick's nuts. Although there are many things Diaz can do to help his situation, he is going to continue to act the way he does until he stops smoking (good) weed and starts getting psychiatric help.
Now, I am not a psychologist or a psychiatrist. But I do have experience working in psychiatric hospitals, enough to have a feel for most common diagnosis which present themselves. In my opinion, Diaz clearly exhibits symptoms of paranoid personality disorder.
Concern that other people have hidden motives
Expectation that they will be exploited by others
Inability to work together with others
Personality disorders are less serious than full-blown mental disorders like schizophrenia, although they do share some traits. Also, this being psychiatrics, many times patients do not have all of the symptoms mentioned in an illness, or present with more. There is much overlap between diagnoses as well. In Nick's case, he clearly demonstrates paranoid fantasies and delusions in interviews, from claiming that people are out to get him and hurt him, to more florid stuff about the government he has expressed on podcasts. Nick also believes he is constantly being used by others and has trouble working with anyone who is not his teammate. Diaz is obviously hostile and easily threatened.
Although it's not up here, the main symptom of having a personality disorder is rigidity. They have a difficult time adapting to situations and will tend to pull out (or miss flights) rather than do something they feel would endanger or compromise themselves. Often, delusional thinking leads them to believe normal sitautions are dangerous or exploitative.
Finally, Diaz smokes weed, and a lot of it. THC is the last thing someone with a psychotic condition needs. Now, I have no idea whether cannabis can cause psychosis (ala Reefer Madness), but it certainly can compound pyschosis, making things a lot worse. Strangely enough, marijuana also contains Cannabidiol, an anti-psychotic compound as well as THC. Cannabidiol is reponsible for many of the medical effects of pot, like nausea relief (although THC also functions in this... double whammy), and can also relieve psychosis, anxiety, and tremors. The problem is, high quality killer weed is stronger in THC and weaker in cannabidiol, while bammer is still strong in cannabidiol but obviously weak in THC. I'm guessing Diaz smokes some green bud, which means he is making his situation a lot worse.
The point of writing this isn't to judge Diaz further, but to understand him more. Like I said, I'm not a professional and I may be wrong. People just need to keep in mind what is affecting Nick and why he acts the way he does. It may have a lot more to do with his brain chemistry than his moral character.