We are always on an emotional roller-coaster. It kind of comes as standard-issue equipment. A cauldron of emotions is always churning around in our bodies. You can sometimes still the waters, but not for long, and it's amazing what can trigger an emotional storm. Up, down, sideways...
On top of the emotions, we have this brain sitting up in our craniums that conjures all kinds of thoughts - rational, irrational, logical, illogical, magical, ridiculous, grave, serious, stupid, you name it. And sometimes one thought follows another, and sometimes it seems the thoughts have nothing to do with one another, and they pop up unbidden, like some weird jack in the box contraption.
And then we inhabit these bodies that have their own purpose and agenda. And we lug these bodies around, and deal with whatever they decide we should deal with. And this is just us. Our beings. Now add billions of other beings on the planet that we need to contend with, and co-exist with, and well, it all starts getting really, really complex.