As I waited to board a flight back from San Francisco last week, I saw a passenger arguing strenuously with the gate agent. Turns out that due to an equipment change, he’d been bumped from his first-class seat into economy. 
I was close enough to hear the gate agent offer him a refund, a travel certificate, and a first-class seat on a later flight. But nothing would satisfy our friend, who became increasingly belligerent and disrespectful at the prospect of not getting his first-class seat.
The word that came to mind was entitlement: “the belief that one is inherently deserving of privileges or special treatment.” Though that passenger’s sense of entitlement was extreme, the truth is that I sometimes find myself feeling entitled: I deserve to be paid X for this project...that person should treat me with more respect…I ought to be able to have such-and-such vacation/car/smartphone.  
When these thoughts pop up, I try to catch myself and change my thinking: I’m not “entitled” to anything. The good things that come my way in life are gifts to be grateful for. This attitude makes it easier to appreciate the people and things around me, and helps reduce my chances of becoming that guy at the airport.
PS: He ended up in economy, in a middle seat no less. Proof that entitlement doesn’t pay!