When I give aviation seminars and classes I often start with the question, "What's the most unreliable thing in a light aircraft?"  Typically I get answers relating to the magnetos, fuel gauges, or the vacuum pump.  While these are often unreliable devices in the aircraft that we fly, they are nowhere nearly as unreliable as the single most unreliable component - the pilot.  Close to 80% of all light aircraft accidents are due to pilot error. 

Of the top 10 items they researched, 3 (including the top two) were related to training.

In addition to training I would suggest that you approach every flight with the idea that you will be constantly vigilant for errors.  You know how you can drive your car home after a busy day and when you get home you wonder, "What route did I take to get here?"  You weren't even thinking about driving.  Your mind was elsewhere.  Don't let that happen in an airplane.  Always be thinking about what is next.  I have a student who taught me a good mnemonic - "If you're not thinking about something, something is wrong."  Always be alert to everything that is going on and never get surprised.  How much fuel will you have upon landing?  Is the weather ahead going to allow you to continue?  Are all the gauges in the green and if not, why?  There are a million things to consider even on a long cross country. 

Basically - keep thinking ahead.

So if you can, take some training.  Be honest about areas where you are weak, and ask an instructor to help you. 

Additionally, make every flight an attempt at perfection.