Linux gives you so much freedom, for example the freedom to fuck your system.
When i was experimenting with bootsticks i typed the following in the terminal:
sudo dd if=bootstick.iso of=/dev/sdb

Where is the mistake? The usb-stick was already plugged in at boot-time and since it was bootable linux mint named it /dev/sda.

You propably already realized it, i wrote the iso the my harddrive. My attempts to restore the partition-table failed, but luckily the kernel still had it in memory and i was able to backup my files via nautilus.
Still, i nearly had a heart attack