You do not have bad days. Some days are hot and the AC goes out. Some days you have to sit in traffic. Some days your boss is crabby. Some days you're crabby. Some days every song on the radio is about everything that's wrong with you. Some days you realize how you've been fooling yourself and some days someone else realized how they've been fooling themself about you. Some days you're broke. Some days the dog bites you. Some days you work your ass off and accomplish nothing.
Despite this, you don't have bad days.
Why, you ask? My day was terrible. Why don't I have bad days?
Because despite all these things, you're not squatting in a bathroom hoping a mortar shell doesn't land on your house. An act of an angry god hasn't washed your home away. You have not been forced into sexual slavery. You do not fear for your life because of your ethnicity. You can speak your mind without fear of government reprisal. You've nothing to bitch about.
I say this, of course, with the presumption that you're from the industrialized north, that you enjoy the privilege, security and equity that comes from accident of birth and wealth of nation. There is the possibility that you are in poverty, in a war zone or have been robbed of your self determination by forces entirely outside your control. If this is the case, you have worthy complaint.
To the rest of you, though, those of you that bitch to no end about your job, your iced coffee or the state of high fashion, really, just grin and fucking bear it.