When life hands you a horribly coded program to maintain, the best thing to do is to make it your own.

Taking ownership initially is scary as all get out.  The current codebase that I'm dealing with is a nightmare, to put it lightly.  But I had to come to terms with it.  I wanted to change it overnight, rewrite it as fast as possible, but due to a complete lack of resources since I'm the sole developer now, well, that's just not going to happen.

So, I move forward.  Each week that goes by sees more tweaks that push it in the direction that I feel it needs to go.  There are some mountains that I simply can't climb right now (register_globals in a 100k+ lines of code is the Everest here), but usability is my primary concern.  It should be security, but due to how the entire system was implemented, it's more of a long-term process than an instant fix - and we need to keep moving forward for our customers.

And while I may not be the best developer on the planet, I can say that I'm aware of the issues software faces.  All software has issues and even the best written code tends to have bugs - especially as that code grows.  Therefore I set goals that can be attained on a weekly basis and make a push to better the system.

Staying stagnant is not an option, and until you take ownership, you will always feel a bit put off by everything - that's normal.  Just get over it and push forward.  After all, you can always blame it on your predecessor.