What's The Stupidest Mistake you've made in Pokemon

Mine was throwing away the Lucky Egg

I lost Blue Version once.

Battling someone with normal type Pokemon with my strongest Pokemon on 3HP and the only remaining Pokemon a Gastly.

I was pretty stupid when I first started playing, so I made a lot of mistakes. My first game was Silver and that got me to play the others. Like my level 100 Meganium still knew Tackle. I also saved after Lugia fainted, not realizing it wouldn't come back. I've learned from my mistakes, and the games have improved too so it's harder to make them. Whew.

Stupidest thing I ever did Pokemon wise was wipe out my friend's team in a versus battle using only a underleveled Tyranitar and a Level 1 Aron lol.

When I used my master ball on a level 37 steelix...ugh.

I once followed a yawn with a spore

I... Oh God, this is embarassing >_<

... I replaced my Mewtwo's Recover with Strength in Pokémon Yellow

I was very young >:l

Oh, I also killed Articuno and saved afterwards, instead of turning the game off. I did the same in Pokémon Silver, I attacked Suicune with my Dodrio's Tri Attack, I didn't think it would make a lot of damage since it was level 39, but I KO'd Suicune.... and saved afterwards... >_<

Luckily I restarted both games and didn't make those mistakes again.

And more recently... I killed a shiny Durant in Pokémon White... I regret that so much ._.

Went up against Whitney and her Milktank under leveled. I'm never getting back those 3 minutes...I regret everything

I have a lot of mistakes, but I can say one: I sucked for raising only my starter and no one else in Pokemon Pearl 5 years ago, and I embarrassed myself by using them and losing against a very good person in my camp.

I'm not going to lie - I've made PLENTY of mistakes in the game. But one of the major ones I remember are:
I skipped lots of trainers in Leaf Green, and then I ended up challenging the Pokemon League about 15 times, it was horrible.. >.>
Also, I was trying to catch Dialga in Diamond, and sense I wasted my master ball by mistake on some other weak Pokemon I can't remember, I had to catch him with regular Pokeballs. I lowered his health so low (because I only had few pokeballs.) that I accidentally made him faint. :(

Hmm,I really can't remember many. Here is a few though.

Running from a Shiny Tentacool in orginal Gold. Did't know there was shinies at the time and was wondering why it had little stars pop off around it.

Yellow,Blue,and Red I never trained my pokemon other than my starter. This is when I first started the pokemon games.....big mistake.

Oh ya,in Pokemon Blue,my first ever pokemon game. I could never figure out why I couldn't get past Viridian City at the start of the game

Traded a Shiny Ralts to my brother for a Shiny Chansey and then restarted the game later. So I effectively got NOTHING OUT OF IT. HURRAH

I picked oshawott...
lol

I was hunting for a shiny Giratina and when I finally found it I soft resetted my game by accident. I also used my masterball on a Graveler. On Pokemon red I killed Moltres. Also when I was playing yellow, I beat the elite four and my game ran out of battery and then the last time I saved was when I was in the victory road...

I've done tons of stupid things in Pokemon but I'll only mention a few. They are all on the DS. My dumbest one is probably in Clairs gym. I haven't saved the game since beating Team Rocket so I was still in the Radio Tower. This is how it went down. I beat the first 2 trainers in the Gym and moved the objects to where it needed to be. For some reason I wasn't thinking and 30 min later I thought I went the wrong way and couldn't get out of it so I turned my game on. I literally forgot that I had to walk down and then right lol. Another one is when I ran away from Raikou (that was pretty stupid) used status decreasers against Pokemon I'm weak against and died, etc.

The only thing I could remember was throwing away my ONLY Masterball to try and capture Wailmer.

here is one. I cant remember the details much though. i saved when i wasn't supposed to(can't remember why) and turned off my game whilst still saving. and when i turn it back on, the saved data was corrupted and erased. It was the first time i noticed the game will corrupt when disturbing a save.

Recently I've been doing several dumb mistakes, such as trying to hit a Ground Pokemon with an Electric Type move and turning off my DS and not saving two hours of game time. Or running into tall grass that has high level Pokemon when I have low level Pokemon and eggs and my first Pokemon doesn't have a smoke ball.

Luckily I've learned all my lessons then. But one mistake that I will always regret which was really stupid was restarting my Ruby thinking it was Sapphire. I seriously cried when it happened; so much work and effort gone to waste augh.