The stupidest thing I have ever done...

I must have been 16 or so at the time. Read all the hot rod magazines, studied all the engine parts in the PAW ad. Thought I was pretty versed in automotive knowledge, even though I had never turned a wrench up to that point. So I ask my older brother if I can change the oil in his Subaru wagon. Oil change-how basic. Too easy-almost beneath my head of textbook knowledge. After some trepidation, he relents. I pick up the oil and filter, a filter wrench and a ratchet and socket kit. I'm on my way now. Time to turn theory into practice. I turn the drain bolt, watch as the crude begins to fill the drain pan, and make a 'mental note' of the oil's strange smell. With no real-life experience to fall back on, it's more of an academic observation. Replaced and snugged up the drain plug, removed and hand-tightened the new oil filter...almost done. Unscrewed the oil fill cap, poured in 5 quarts of 10W40, then tightened up the oil cap. Job well done. Just added a skill to my repertoire. Hell, I just created a repertoire. Anyway, I start the car, and the engine starts to stumble. just a coincidence. Couldn't have been anything I did. Brother takes the car to a mechanic. Simple diagnosis: There are 10 quarts of oil in the engine and no oil in the manual transmission. Self-esteem: gone. Resounding shame: still with me.