By the time you're 35, you should have successfully done following at least once:

1. rm -rf / on your unix or linux box
2. Reboot production server by mistake
3. Drop CPU/hard disk and damage it permanently
4. Changing firewall rule instantly blocked you out
5. No backup was made/verified ever...
6. Delete source code before actually committing to source control
7. Run a SQL update/delete with wrong where clause