Hacking I think I bricked my 3DS.

[UltraSUPRA]

I pressed the power button, the blue light came on, and right when the light was at full brightness, it shut itself off.
Either I did something stupid while downloading CIA files (probably not, my system was closed last time it ran out of power and nothing was downloading) or it has something to do with falling off of my bed.
I think I backed up my NAND, but I'm not entirely sure.

 

[flzmx]

It's probably something to do with falling off your bed.

 

[E1ite007]

Does the SD card is being read correctly? That could be the problem if you never installed boot9strap or Luma3DS to the system's NAND.

 

[TheNintendoEnthusiast]

Hey! That is when the system is looking for a firm file to boot to but can't. Try reseating your SD Card. You should be good after that.

 

[TurdPooCharger]

Try the battery trick. If that doesn't work and the 3DS still instantly shuts off, that means you likely torn one of the flex cables in the hinges (ie, top lcd, camera, speaker assembly).

 

[UltraSUPRA]

It's probably something to do with falling off your bed.

Hey! That is when the system is looking for a firm file to boot to but can't. Try reseating your SD Card. You should be good after that.

So I think I get the story now.
When my little sister Emma pushed my 3DS off of my bed, the SD card got slightly dislodged.
After we retrieved it, and I turned it on, and it shut itself off, I was confused.
Now that I knew the problem, I asked Emma where the screwdrivers were. I got one and went to work.
The SD card was still in the slot, confusingly enough, so I pushed it out and then back in.

It booted back up.

I'd like to thank everyone.

 

[flzmx]

That is when the system is looking for a firm file to boot to but can't. Try reseating your SD Card.

I'm going to say that's personally why my 3DS is bricked (SD card slot came loose internally), reseating the SD card seems annoying though. As a temporary thing, I used to just take out the SD card and put it back in until it booted. Nowadays, it just doesn't work at all.