Firewalls

well I had bad experiences with firewalls, I use to have zonealarm free version , but got tiered of it because of all the configuration that needs to be done, and I heard how many of the firewall solutions caused problems to applications even if you add the required exceptions, so I just stick with my anti-virus and anti-spyware software, and try to becarefull who I connect to. I usually have windows firewall disabled too.

So far I have no problems, why do I want to run a firewall? I assume because to protect your computer from being hacked right? or someone trying to ping you to death ( Denial of service attack ) , as a normal user at home I don't feel at risk, or should I?