"A lazy man carries a dull knife".
This old adage explains pretty concisely the proper habits of a man. To have a sharp knife is to care about the little details. In that phrase you can see the depth of meaning that it carries, in that that attention to detail should spread to all facets of life. It shows that you are in fact in control of your life. It's like having shined shoes. You care, and it's evident. Seeing that laser like glint of silver on the edge of an age-darkened steel blade is a badge of respect among those who know, and now... so do you.
In more practical ideas, a sharp knife is a SAFE knife. This seems backwards, so let me explain: the duller your knife is, the harder you have to push to cut something. The more force you have to exert, the less control you have. This means, the duller your knife is, the LESS control you have over it. When it comes to sharp, pointy things, you want as much control over them as is physically possible, so keep your knife sharp.
Now sharpeners come in all shapes and sizes, from the most intricate angle setting setups that run into the thousands, to those little cheap jobs with the carbide blades that you pull your knife through (please PLEASE don't ever use those... they kill knives). The oldest and simplest still around is the stone, and they too come in all different sizes. We as outdoorsmen want something that will handle a full sized knife, as well as our pocket knife. Something that can handle super-steels and carbon steels alike. Something that we can carry on us either in bag or pocket and not be a burden. It's all a trade off in size vs. weight. THIS is that stone.
Spyderco started in the sharpening business well before they started making knives, and boy do they know how to make a sharpener! I've spent years searching for a stone that can go in my pocket (or more recently in my PocKit) and the Spyderco Double Stuff is the culmination of that search. This easily pocketable stone is actually two stones stuck together; the grey side being a medium grit, and white being a fine grit. I say stone as a common vernacular, but it's actually a misnomer. The "stones" used are actually ceramic (the same formula as their well regarded Sharpmaker set), with sapphire embedded. What this means to you is that it can handle ANY steel with ease, and my favorite part: you don't need to use a lubricant! Once the stone is loaded up with steel (and it's pretty easy to notice), you take it to some water, add a little comet and scrub the grit away. It takes a good while to reach the point of cleaning, and that makes it perfect for on-the-go use. The 5"x 1" stone can handle your favorite bush knife in a pinch, but it's handy enough for that jack knife in your pocket. It carries in a split-grain sheath that makes a perfect strop when the stone in inserted, so you have the complete solution all in one handy kit.
I love mine SO MUCH, it's with me all the time (much to my chagrin sometimes because EVERYONE knows that fact, and I end up sharpening a lot of knives for friends.. but that's another story).
Do yourself a favor, and pick one up. This is probably going to be the LAST stone you'll ever need to buy, and with the amount of times we use our knives... that's saying A LOT.