Ignorance is less blissful than advertised
The usual tacit way of explaining this in a roleplaying community is simply that the main story is a non-entity. It couldn't have happened to your character specifically because then every roleplayer past and present needs to accept that it must have happened to one specific character. Thus, it just didn't happen. Simple, right?
The problem is that, realistically, these are events that would change a person. SWTOR is unique only in the sense that it codifies all of these changes via the myriad decisions a player makes as he or she levels up a character. It's clear that things took place, sometimes major ones. Here's an example from the same game: As a Trooper levels up, more rank-related titles are unlocked. There has to be some reason why the character keeps rising in rank, naturally... so do you just ignore it? Pretend it was always there? Come up with a totally different explanation?
More to the point, several things that happen over the course of most game storylines would have a profound impact upon player characters. If you played a Forsaken back when Wrath of the Lich King was out, your entire stated purpose of being was to destroy the Lich King. You cannot, logically, leave that out of your character motivations. This is a lore NPC with an absolute need to be relevant to your character. So you get together with your friends, work your way up to the final boss, kill him... then what?
Do you pretend you didn't kill him, cutting your character off from the resolution of a major and implied personal arc? Do you make it clear that you did kill him, thereby implying you alone should get the credit? What are you supposed to do in a situation like this? Ignoring it doesn't fix it, but neither does paying attention.
A quick aside for the members of our audience preparing to write up an explanation of how this proves player-generated stories are better: You'll get your turn in a week or two. Settle down.
What we need is a solution that allows a character to interact with the main storyline while still maintaining enough distance that you aren't locking other people into your own version of events. So how can you manage that?
First method: It's a big country
The one aspect I like about the Star Wars universe is the implied but not stated fact that the galaxy is always in danger. There are enough people around and enough insanely powerful technological devices present that there is always someone threatening it. The films just show us one tiny snapshot of a period in which the galaxy faced a specific danger, and for that matter, there were other major dangers most likely not even seen then. You don't have to go far to find a maniac to threaten people.
How is this a good thing? Well, it's not if you live in the universe. But if you're adventuring in the universe, it's largely functional as a "Get Out Of Uniqueness Free" card.
So you didn't save everyone from a specific menace, but there's enough space for a menace to exist. Maybe you aren't the last in the line of the Dragoons as the advanced job's intro quest implied in Final Fantasy XI, but you're certainly one of the few. There are points of a story that are broad enough for you to file off the details and leave in the important points.
Sometimes, however, this doesn't work. Let me get back to the Lich King example above: You can't say, "Well, I didn't kill the Lich King, but I killed a Lich King." You're going to need something else.
Second method: It takes a village
In fiction, we like to have the lone hero. In reality, that simply isn't the case most of the time. With a handful of exceptions such as the actions of Captain Chelsey Sullenberger, heroic accomplishments are usually the work of several people against several other people or a force of nature. So if we're butting up against a need for several people to make a single accomplishment, why can't we make use of that fact?
Your character must not have fought the Lich King. But really, if you think about it, the battle against him wouldn't make sense as a one-on-one duel, nor as a one-on-ten duel or any other permutation. We're talking about a clash of armies, followed by a surge up the tower and a final battle that consisted of a whole lot of people fighting and dying. And there is absolutely no reason why you could not frame yourself in these events.
The satisfaction of a complete character arc is still there. You might not have dealt the killing blow, but you were a pivotal part of it. But you aren't creating a scenario that locks out other players from the story.
Third method: One detail amidst hundreds
Let's say that for whatever reason, neither of the above is working. That's when you have to go back to a technique that I talked about long ago for handling character adaptations: Distill the essence, then build something new on top of that.
For lack of a better example springing to mind, let's use the Teron Gorefiend quests from World of Warcraft, since they're an old and familiar element to many people. You wind up doing several quests for an orcish spirit to retrieve Gorefiend's various artifacts, only to discover at the end that the spirit is Gorefiend and you've just inadvertently freed him. Let's further assume that this has a big impact on your character for whatever reason.
You can't say that there are a lot of former Death Knights somehow managing to trick people into recovering their artifacts; there's one. And you can't say that this was a multi-person effort because this whole operation sort of hinges on surprise and subterfuge. What do you do?
Well, you figure out what about this incident meant so much to your character. Maybe, for instance, you're playing a Draenei and you realized that you just wound up helping one of the historical enemies of your people. In that case, construct something else, something similar but still distinct. Maybe he was gathering magical remnants that he realized belatedly were fueling Blood Elf research. Maybe he took a fairly standard oath to escort a prisoner to safely only to find that it was a Fel Orc. Whatever the case, you can build a decent story that happened offscreen with much of the same emotional impact but not the specific traits that might invalidate other people's experiences.
Fourth method: Fine, ignore it
Yes, this is last but not least for a reason. I'm not saying that tacitly ignoring this stuff doesn't work. Just saying that it shouldn't be your first stop.
The mail address is still firstname.lastname@example.org for any feedback or comments, or you can just leave them down in the field below. Next week, I want to talk about player psychographics and how they fit into roleplaying because you'd better believe they do.
Every Friday, Eliot Lefebvre fills a column up with excellent advice on investing money, writing award-winning novels, and being elected to public office. Then he removes all of that, and you're left with Storyboard, which focuses on roleplaying in MMOs. It won't help you get elected, but it will help you pretend you did.