Ah, yes. This is one of the most unforgettable experiences I've had in my childhood.
It all started way back in Gen 2. Pokemon Silver. I was so excited with the game, loved the new MC's sprite and then picked Hinoarashi as starter (Cyndaquil's Japanese name) because he was so cute and cool first time I saw him. I was feeling so great, happy, and awesome at the same time. I've managed to solve the Unown puzzle quickly as a noobish pokenerd-to-be with a fat gameboy and 4 pairs of batteries to spare.
Winged the first two badges then reached Goldenrod. At that time, Quilava was my only strong pokemon, proudly defeating my Rival's Croconaw without even losing more than half it's health from Water Gun. However, when I entered Goldenrod's gym, I was brutally beaten by Whitney's Miltank, and even single-handedly. It was my earliest whiteout in my pokemon gaming records ever. What was to blame? ROLL-freaking-OUT! Oh, my poor, lovely and awesome Quilava...around 6-7 levels above...wiped out in 2 hits!? WHAT?! wtfomgdatpokemooisOP!
...and that, my friends, is when I came up with Smokescreen/Sand Attack+Supersonic A strategy I desperately relied on as my last resort to avoid endless rage...I mean weeping... err... training. From then on, I've been carefully saving at least one slot for a "utility move" among one or two of my Pokemon.