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