Same, but I forget way more than just once.
Forgeting i didnt plug in the power expander batterh and then yell at my programmer for the flywheel not working
I put a plier in the power expander to straighten the pins while the bot was still on. It sparked:/
rip
Forgot to remove the autonomous code and caused the robot to fall over at the beginning of the quarter final match. Got the stink eye for like 5 hours. Oh well, it was just the first competition of the season
We removed our IME cables from our robot in the semi-finals. Our robot just went straight and into the wall 
The base just freaked out for the whole match and we lost.
For those of you who haven’t seen this.
Not practicing a lift before the match.
Using nylon rope over chain for the entire skyrise season on a linear lift robot. Took 30 seconds to get to full height.
Rip… rest in peace
Earlier this season we didn’t put motor controllers on our robot and were wondering why our motors were moving with no input. It took us, another team, our mentor and our teacher a few days to actually realize…
Tried a high hang on a prototype without our backup battery. Pushed it past the clicking. Rip
Our first year we tried to program a gyroscope in easyC for our autonomous. Then it kept our autonomous from running for about 2 months.
yet we still made it to nationals…
Using a cube, to push down our intake during a match…
rip
we kept forgetting to save the code. we are coding on an old laptop with a dead battery so if someone accidentally unplugged from the wall it it would turn off not saving our code. this caused us many problems at nationals as at the UK nationals everyone is fighting for plug sockets so stuff inevitably gets unplugged.
that is so much like us, our one is pretty old
That’s why we always bring extension cables (maybe more than one, I don’t know. I don’t pay attention to these things.
Having 5 teams is also a big plus, as we usually get an entire row of pits to ourselves, so we don’t have to share with anyone
Through years of programming, I have developed the habit of pressing control-s after pretty much every line I write. I suggest any programmer should develop that habit.
I have as well. It helps more than it hurts, but sometimes a major code change that doesn’t work hurts too 
always trade offs. I mean, I could set up backups, but ehh.
<sidetrack class="10% relevant">
You could even set up autohotkey to do something like alt+s saves to a second file; the backup. After every working iteration, save to backup. After every change, save to primary.
</sidetrack>
That’s what git is for
Git only helps if you upload your code after changing it, so you still have to save (and then remember to commit and push) 
Also as a side note, many modern IDEs and code editors include autosaving functions. For example…