It all boils down to practice and repetition and knowing how RTH works.
I bought my first drone --- a Phantom 2 Vision+ --- in July 2014 and didnt want to fly it more than 200m from me when I first flew it. Eventually, once I got comfortable with the controls and flying by FPV live video, I was able to fly out a mile or more using my FPVLR booster kit. Once I got my P3P, I was fully hooked on long-distance flying and now I can fly out 3 miles and back on a calm day without breaking a sweat, and that's using stock batteries. Of course, there are extremists out there with battery mods flying out 10 miles and back, so the long distance addiction can get nuts!
The most important thing is to always survey your surroundings to look for hazards, as well as do pre-flight research on Google Maps. Any time I fly somewhere new, I always check the anticipated flight path on Goog Maps and see where the cell towers and high-voltage power lines are. Also look for small airports since they can be hidden away from main roads. Once you know where those are, then you can confidently head out into the great blue yonder and trust your FPV and telemetry to guide you home.
If you get hooked on long distance, then I would suggest buying a real-time GPS tracker such as the Flytrex Live 3G. Sometimes when I fly out really far I will lose FPV and telemetry, even when RTH is activated and I'm confident the bird is on it's way home. It can be really nerve-wracking when you are 12,000 ft. out and you have NO info. that the bird is flying on a straight line back to you! At least the Flytrex Live 3G will tell you it's coming home and you can breathe easier
