I'm new to Linux and I made a big mistake at work recently locking myself out of our own server .

I did iptables -F first as the tutorial said and then entered the rules. I wanted to start over again so I did iptables -F and it locked us out. We had to get someone to physically restart iptables before we could get back in.

Any idea why the second iptables -F locked me out and how to avoid it and know when it will flush everything and when it will lock out?

Thanks

I used some rules I saw in a tutorial as follows:
iptables -F
iptables -A INPUT -I lo -p all -j ACCEPT
iptables -A OUTPUT -o lo -p all -j ACCEPT
iptables -A INPUT -I eth0 -m state --state ESTABLISHED,RELATED -j ACCEPT
iptables -A INPUT -p tcp --tcp-option ! 2 -j REJECT --reject-with tcp-reset
iptables -A INPUT -p tcp -I eth0 --dport 22 -j ACCEPT
iptables -A INPUT -p udp -I eth0 --dport 22 -j ACCEPT
iptables -A INPUT -p tcp -I eth0 --dport 80 -j ACCEPT
iptables -A INPUT -p udp -I eth0 --dport 80 -j ACCEPT
iptables -A INPUT -p tcp -I eth0 --dport 53 -j ACCEPT
iptables -A INPUT -p udp -I eth0 --dport 53 -j ACCEPT
iptables -P INPUT DROP