Emotions are a universal thing across advanced animal life (At least in theory) and I was thinking on the possible reasons for emotions existing as I reasoned they must have some purpose for existing, I have many ideas but I shall hear from the rest of you and interject my theories as they go along

to get any debate going.
Humans and animals are affect driven, affect is an idea attached to emotion or strong emotion, more rationalising than reasoning, that is deciding on the basis of these affects and "explaining" their thinking after the fact, there's a whole bunch of complex explanations of why this is so, its been the word of psychology to do so since the early days even pre-Freud.
For the time being some evolutionary psychologists have the best explanations I can think of, ie that our cognitive brain, is a recent innovation, for much longer, probably the greater part of human history, we've been reliant on the older "serpentine" brain, under stress, in crisis or under threat, it kicks in, some people are more reliant on that part of the brain more than the cognitive part, lesions, brain chemistry, it all matters, anyway, affects, particularly strong affects, can compel behaviour quicker than cool headed reasoning, for the greater part of human history I think that's been important to survival so its that which gets passed on the following generation, evolution has selected for it and maybe carries on selecting for it.