Back in Yesteryear when Command and Conquer: Red Alert 2 was popular I was pretty good against the computer, never lost a match against my brother and was a reasonable opponent to my friends in LAN games.
One day I decide to go online, I start building up my base, put down a couple of defenses, and 30 seconds later a column of approximatly a million tanks steamrolls through my buildings and anihilates me.
I stuck with friends and computer opponents after that.