I concur with woodmills. I'll also add that most of my chainsaw use is far away from the convenience of electricity - maintaining trails, building foot-bridges, dock repair, and even firewood.
I also find it rather serendipitous that at about the time I’m getting tired of sawing, the chain needs sharpening. We all know that a sharp chain is safer than a dull one. Consider also that actually taking the time to sharpen the chain provides the operator with a chance to sit down, catch a breath, and relax (because noise causes stress, too).
Technique is something I learnt from my dad. In fact, whenever there is more than one person involved in the cutting operations (almost always the case when we’re in the middle of nowhere), sharpening can be simplified. One person sits and braces the saw against them while also controlling the chain (holding it when sharpening, and moving it to the next tooth). The other sharpens. When I’m alone, I find I can get one side done by holding the saw myself, against my leg. The other side is a bit trickier. You can prop it against something, or sink it into a log to hold it. Every 2nd tooth, I'll give the file a wipe (much to the chagrin of my wife) on my pant leg.
I bring (besides gas and oil) a small tool kit with me that includes:
the sparkplug/screwdriver tool
2 files
a spare chain
a special grease gun for the bar
a stiff-bristled paint brush
a rag
and finally, a tourniquet.