I think the key is to recognize, accept and then dismiss the 'negative' emotions (quotes to show its a lable, not a TRUE descriptor). Anger, disappointment, depression, sadness etc. can be necessary moments in life, overcoming them doesn't mean completely eschewing them, but rather not dragging them around with you like some piece of extra luggage you tried to get through baggage check but the dude at the counter wanted an extra $75 to put it on the plane. I mean, you never know when you're gonna be stuck with flight delays, or have to change gates at the last minute... or run through the Istanbul airport at full speed to make your connecting flight.
That extra piece of luggage quickly defines the whole experience. Let that shit go!