When I first realized this many years ago, I was quite shocked by the truth of the statement. As human beings, it is our job to assign emotion to everything and everyone in life. The connection of emotion is what makes us human. Our emotions filter our interpretation of truth and fact. If I was to say: the sun was a bright pinky-yellow this morning as it rose, many of you would conjure some type of emotion associated with a past sunrise that you encountered, thus your interpretation of past sunrises is painted with your version of the truth of those sunrises.
It’s pretty harmless to have your own filtered version of a sunrise, however, where we can get in to trouble is when we take life affecting moments, immersed in emotion, and consider our emotions around those moments’ facts. It is easy to get in a 
cycle of over-thinking about a person, event, or issue when there are a lot of conflicting or overpowering emotions involved. We get sucked in to thinking our reality-filtered by our emotions-is fact. Our reality is not necessarily the reality we should be taking in to account. Our emotions tug us in the direction of a heart’s desire or a financial need or a family burden. The need or want attached to those things give us a distorted version of what is. Our minds trick us in to thinking the feeling-filtered perception is fact because that is easiest to believe. Face it, as humans we are very attached to our feelings and we are all, to a degree, egocentric. “My ideas, ways of doing things, beliefs are the best…” If we didn’t buy in to our own beliefs and patterns we would be wrecks.
What do you do then, when you may be in a cycle of over-thinking or uncertainty over some emotionally charged issue? You aren't sure what is fact and what is your emotion-induced fiction, swaying you in the direction of your heart? You journal. Get out your Traveler Notebook and start writing down the emotions you are feeling, the raw facts you know for sure, your perceptions of the facts, and any feedback you might garner from close associates. Add it all up, sum up the information, write from a third person perspective, dispassionately with neutral observations, then take a step back. Leave it, walk away, let the thoughts settle. Ponder them on a long walk, over a hot cup of tea, remember to believe in your own best self and return to your written words. You will, I promise, have gained a perspective. Write it down, the unfiltered perceptions and why your emotions tugged at you so much. Remember however, even though feelings are not facts, they are what make us gloriously human, so beautiful and fragile, and each emotion is worth feeling and savoring.
Just thought I would share a little technique I share with class participants that helps people refocus when they are caught in a cycle of obsessing about something or they know they have a 'button' that gets pushed. "Pocket Therapy" is a loose term, obviously it is NOT therapy but it is fun and mine has actually worked for me the couple times that I have pulled it out and looked at it.
The idea is simple, take a small matchbox of some sort. You can decorate your matchbox any 
way you like. On the front you are going to put the word or action that you get stuck in a cycle in....see my pictures of mine. On the inside you are going to write your 'therapy'...your quote, your thought that gets you to stop and refocus your mind. I also put a quote on the back of my box that was relevant to my issue - which is over-thinking 
something. I keep my box in my bag that I carry every day to and from work. Will it 'cure' a big issue or solve all your problems? Of course not, but sometimes all we need is a little reminder that our thoughts are not facts and refocusing can be a simple step to finding inner balance again.
I love that quote because it speaks so well what I learned many, many years ago and that is simply that happiness is completely in our control, our choice. We decide our attitude everyday, we decide our guiding emotions...Did someone cut you off in traffic, did your coffee you spent $4.00 on taste terrible, was someone rude to you when you got to work? All of these kinds of things can set you up for "well I guess this is how my day is going to go" syndrome. We can choose to let those kinds of things dictate our attitude and joy (or lack thereof) the rest of the day or we can choose to realize that our very existence on this big blue ball is a miracle and all those little thing really do not merit wasting time being upset or mad.