I usually order some Korean BBQ and indulge myself to ice cream to get rid of the blues. 'Cept you're talking about severe depression... Just don't start drinking or taking drugs.
Even if Goku loves fighting, I don't think he would kill someone like Superman. The same goes for Superman, I don't think he would kill someone like Goku.
I believe so, it's like getting your certifications. Such as Ciso, you have to take the exam every 3 years, or like Microsoft (that's everytime they upgrade). My major is Network Systems Admin and so...