Today, my training plan called for a hour long fartlek on hilly trails, easy overall but attacking the ups.
There’s something joyous about fartlek sessions. You don’t have to clock watch or aim for a specific pace, you can pick and choose your efforts and recoveries to suit your mood and they seem to lend themselves much more to random wandering than other runs.
So tonight, I headed for a car park somewhere on the North Downs, and then meandered hither, thither and yon, following footpaths as they appeared and not worrying about sticking to a predetermined route. I spent significant swathes of the run unsure of where I was, if not exactly lost, and swapped well-manicured tracks for little trails through the woods. There were mini hurdles, u-turns galore and blissful solitude, and by the time I found my way back to my car, I was grinning.
To steal a line from James Adams*: this is why I run.
*Author of Running and Stuff. Read it!
abradypus 
Sounds great fun!
I love fartlek sessions! They are a great way to push yourself but without the pressure of having to reach a specific goal, and really good training for races when you need those short bursts to get past people. 🙂
Ooo I need to do some sessions like this, if you ever want some hill running company give me a shout!