I'm sorry, but that's a stupid assumption to make.

I'm "only" 29 and last year I managed to catch a parvovirus B19 from someone - it's a virus that's relatively common in children, but has very mild symptoms - it's almost unheard of in adults, mostly because you either already have immunity, or there are no symptoms/the symptoms are no worse than a mild cold/flu. Well, except that in about 10% of adults it causes severe response with a high fever that last weeks, with arthretic swelling of joints - and in 10% of those the joint issues don't go away for years. Well, it's been nearly a year now and my knees and other joints are still fucked from the virus, I'm constantly on steroids just to control the inflammation.

So no, this has changed my "I'm young so I'll be fine" outlook on this - the chances are not always in your favour.