When I was 35, we vacationed in Europe for a week, and it was the first time I had left North America. I realized that I was closer to 40 than I was to 30, and I quietly made a goal to visit every continent by age 40.
Two years later, I'm no closer to completing that goal, although I still think about what it would take to make it happen.
Sometimes I think the goal is unrealistic, and I know that this is an attitude that makes it just that: unrealistic.
Others have even more ambitious goals, like seeing every country in the world. The dude at this link claims he's 149/192 countries into his goal, which he hopes to complete by 2013, his 35th birthday: http://chrisguillebeau.com/3x5/places-ive-been/
Bottom line: the world won't come to you. If you want to see the world, go see it. Make it happen.
And with the purchase of a 6-continent ticket, it looks like most of the goal could be knocked out in one trip. Cost for such a ticket: about $7000.