The human animal is blessed with several senses, all of them pretty sharp.
Now while we can't see like a Kestrel, we do have excellent binocular vision in full colour. Our smell may not be up to the level of a bloodhound but still passable and will detect things only our subconscious is aware of. Bats may have the edge when it comes to hearing but our own ears still allow us to pick up even minute sounds and triangulate where it came from pretty accurately giving us a 360° awareness.
Like everything else, our sense need trained. Never forget the catchphrase "Use it or Loose it". While this is usually thrown around in the fitness industry where they're talking about cardio or muscle mass. Here I'm talking about your natural senses, all 6 of them.
Hold on there! How many?
That's right 6, and no I haven't lost my marbles, nor am I into any mumbo jumbo mysticism. Here are your 6 senses, in no particular order:
1- Sight. Simply, if you don't see it coming, how can you deal with it? Constantly scanning your surroundings will keep you out of trouble, reading body language can deescalate a situation and seeing a punch coming may keep you from getting knocked out.
2- Hearing. A 360° sense, if you loose the iPod that is. Keep your ears open and they'll complement your eyes in preventing you from getting into a conflict in the first place. Plus if you're in the ring, it's nice to be able to hear the coach calling instructions.
3- Smell. Not as useful in combat as the previous two. Although it's not uncommon to hear an old soldier or old doorman say something like "I can smell trouble in the air". We do pick up pheromones and hormones via our sense of smell, although we can't consciously smell them it often registers as a gut feeling, the hairs on your neck standing up. Trust in these instincts and you may live to fight another day.
4- Touch. In the heat of combat things move too fast to see everything, this is where touch comes in. Grapplers, Wing Chun, Tai Chi and Eskrimadors all train their touch sensitivity to a high degree. Learning to feel your opponents movements will tell you not only his intentions but also show his openings.
5- Taste. Smell and Taste are actually two senses that are closely linked, we taste the air, maybe not quite to the level of a snake, but we do pick up those pheromones we mentioned earlier. This is the sense you don't want to use unless it's really hit the fan! Biting, while nasty and "dirty" is sometimes inevitable.
6- Common. Ahh, common sense, the much misunderstood 6th sense. If only more people would tap into this resource I'm sure the world would be a happier, healthier place to be. It is this sense that puts the others in order and interprets their signals into usable info.
While they are listed in no particular order, I did save the best till last, Common Sense. In the ring, common sense says cover up, move, stay out of the corners and hit him harder and more often than he hits you. It says train harder for longer than the other guy.
For self defence it says, the lights fading remove the sunglasses and iPod. It says, the atmosphere in this bar is a bit tense, lets move on. It says, apologise to the guy that aggressively bumped into my shoulder, I've no need to get into fisticuffs.
It says, eating sugary food will make me fat and lethargic, it says that extra pint will make take away any hope of controlling my body, and will leave me destroyed tomorrow. And more.
Try to keep your senses sharp, practice using them and don't take them for granted.
If you look at a computer screen often, take regular breaks to focus on something further away. There are muscles in the eye that need trained, just as you would train your biceps. Try this exercise used by Yoga and Chi Gung practitioners alike:
Hold your finger a few inches from your face and focus on it, now without moving your eyes, focus past the finger onto a distant object and back again.
For the ears, spend a few minutes quietly sitting, close the eyes and focus solely on listening. Try to recognise as many sounds as possible, especially the real quiet ones, try also to put a location to each sound. You can check how accurate you are afterwards.
Touch, there are many specialised drills such as Chi Sau, Push Hands and the like that specifically teach you to use touch sensitivity to move with an opponent. If you find yourself in a grappling/close range scenario, attempt to relax and not to use brute force to control the situation. It's best if you seek out a qualified instructor to take you through the finer points of sensitivity training.
Taste, well in order to really enjoy your food, you want a good sense of taste. The simplest way, cut out the crap food and the cigarettes, instead find subtle flavours and foods that stimulate as well as refresh the palate, same applies to smell as the two sense are so closely intertwined.
So there you go, a quick guide to your senses. Take the time to appreciate them. In the RBSD circles they come under the heading of "Soft Skills" i.e., skills that do not require either hitting someone or lifting something heavy. But like the skill of hitting hard and accurately and the skill of lifting heavy, consistent conscious practice is necessary.