The idea is to make your systems and networks a little harder to break into than your neighbors. They won't keep bothering you unless they have an easy way in. It's like having someone walk down your street checking door knobs. Locking your doors will keep most out. ONLY thoughtful administration can limit the vulnerabilities.
Security comes at the price of convenience.
So, you need to balance your need for security with how much ease of use you are willing to sacrifice. Don't try to avoid risk. If you try to protect everything with elaborate security measures, you're likely to miss little things that will result in security vulnerabilities. Think about security before you implement something. Trying to secure after the fact is difficult at best.