I have thought long and hard about ideas like this, mainly because I am passionately interested in consciousness research.
Competition: our natural biological tendencies have evolved to create the competitive nature found in humans. This is because in nature, there is always competition. However it's not about who can take the prettiest picture, it's a competition to survive and raise your offspring. Think about it, why do we compete now? To win obviously. The kicker is that we're constantly reinforced because it 'fells good' to know that you are better than someone else at something. It feels good because of the chemical signature behind all emotional states; they are positive reinforcement that encourage us to continue the behavior that will create this happy feeling. This was an advantage in our history, because when we were in the 'struggle for existence' a hundred thousand years ago, winning a competition meant food and survival. Thus the consequence and reward for being competitive is a feeling or emotion produced in your body, and it's the same emotion that you get when you compete in art, sports, or anything else. The interesting part about this, is that we are no longer in a struggle for survival with the rest of nature. Our populations have grown exponentially, and the only predator to the Human being, is the human being itself. Thus we can't ignore the truth. When we are competing for that good felling we get when we compete and win, it's simply an ingrained biological impulse that that has evolved through the historical record.
"If you compete with no one, no one can compete with you."
Comparison and external validation are along the same lines as competition, which are natural impulses driving the behaviors. Although these terms can sometimes be ambiguous, they inevitably lead to a change in your emotions and feelings, that either negatively or positively reinforce your behavior.
What I think, is first be aware of how each of these words relates to your emotional states attached to them. Second, don't let them be the guiding impulses in your life's path. For example with photography and other art, my number one reason for doing it is for my own sake, because I am happy doing it. I never look at art as competition. Comparison however I think is not a bad thing in photography in of itself. Comparing allows you to view different perspectives of styles, and get a sense of the different thought process amongst other photographers or what not. External validation is tricky, but for me I can't deny it feels great when people compliment you. Just be aware, and don't rely on this way of obtaining that 'good feeling'. Because truth be told, you can access that extremely happy emotion felt when someone compliments you, by other means.