After reading Megan's post on Forbearance about how great players strive to learn and master new specs or classes rather than be content and lazy with their characters, I wanted to write a lengthy response involving WoW psychology and the benefits of consistent neurological stimulation, but I quickly realized that even I would probably stop reading if someone's comment was that long. TL;DR to the max.
As a college student, I have learned a fair amount in my academic career: from figuring out how to tie my shoes in kindergarten (bunny ears FTW, I still don't know how to loop, swoop, and pull) to ascertaining the molecular basis of cystic fibrosis (a genetic mutation leading to a malfunctioning/non-functioning chloride ion channel, what son?!).
No matter the subject material, the process of learning never changes: converting an external stimulus into coherent information that can be processed and stored into the long-term memory, theoretically through the biological mechanism of long-term potentiation. What we experience consciously, however, is that the more we perform a task or are asked to produce an answer to a question, our performance in these areas improves.
For example, think about any part-time, food industry job you've ever had (if you've never had one, you're a bastard); not only is it crucial to know where the burgers are in the freezer, but also how many can fit on the grill at one time, how many to cook to meet any present or future need (without letting them sit under the heat lamp too long), how long they take to cook, where to put them when they're done, etc. Eventually, when cooking burgers has been burned into your brain (no pun intended), you can manage the deep fryer and all of its aspects, and then the dressing table, fry cooker, ice cream machine, coffee maker, drive thru, and register.
How long this mastery takes varies on an individual basis, but I'm willing to bet you have all experienced the mastery of a task and the utter boredom, disinterest and apathy it creates.
"Whoops, I dropped a tomato in the deep fryer... Cool, look at it sizzle."
Let's tie this back into WoW:
Leveling a Ret Paladin is easy (arguably the easiest spec to level as a paladin). Gearing up by running heroics and farming mats, still relatively easy. Of course, playing a Ret can be a blast. Hell, this blog wouldn't exist if I didn't think Rets were fun to play. But what happens when Rets become the "flavor of the month" because people learn about some bug that may or may not make you an invincible and vengeful god, and everyone and their brother reroll? Well, simply put, you're no longer that special, tiger. Now you have 44573443565 other Rets (not to mention DKs) to jockey with for a spot in that heroic daily group. Why would someone pick you over those other guys? At this point, it simply becomes a 'First come, first served' or, worse yet, 'Who's name is cooler?'
Speaking of names, I swear, my old raid leader never pronounced my paladin's name right.... it's not an-TEE-jen, it's AN-teh-jen. Whatever, hatchet buried, bridge built over the water, blah blah blah.
You could market yourself, making an absurdly-long macro that automatically posted your 'DPS LFG Heroics' with a personal touch like 'will trade sexual favors for guaranteed spot' (someone on my old server, jokingly, had something along these lines in his enchanting macro... it worked, he got tons of business). But seriously, how many times do you see a wall of text in trade chat and just completely ignore it because you half expect it to be some 'jOiN mY gUiLd, We HaVe A tAbArD!!' bullcrap? Too many times, my friends.
You could take Megan's suggestion and diversify your playstyle. For paladins, this can be difficult, but the end result is the ability to fill any roll whenever you need to. Healer just drop group? Respec holy and have fun playing whack-a-DPS. Tank d/c? Respec prot and 969 your way to victory. Versatility is the name of the game here, folks.
Of course, I'm not saying that being good at all these specs will make you a better person. We all know rolling a paladin does that automatically, so no need to fret. But the willingness to change and not be afraid of failure, to be a noob again and learn how to do something completely different, that... that is invaluable.