What is pain to you, that it makes you fearful of it?
Pain is one of the most effective destroyers of momentum in living our lives. It can destroy motivation, hinder our ability to concentrate and think clearly, and block or veil our senses and so prevent us from perceiving our environment correctly and interacting with it effectively. Since it makes us feel bad, we fail to radiate positive energy, and our surroundings respond correspondingly, drawing the general mood into a downward spiral.
Since pain is often an effect of bodily sickness, fear of pain usually extends to fear of falling ill. And it's not just the accompanying pain that makes illness something to avoid: there's also often an anxiety that it may be 'serious', that it might hamper one's subsequent life by leaving some permanent damage (even the possibility of minor impairments can cause fear: some people are afraid of a strict dietary regime), or even might be terminal.
Observe, however, that this type of fear arises rarely in situations in which there is direct evidence that an illness is serious in this sense; rather, when it is clear what's to expect, people are often calm and composed. This suggests that it is more often the unacknowledged possibility, suddenly coming to consciousness, which disturbs, while a more composed stance comes into play when the actual course of future events is predictable.
Sometimes people report that a sudden heavy illness has transformed their lives by making them aware of the fragility of good health, and the uncertainty of their future in general. (Although in truth this is a little dishonest, for they knew about that all along for some time before; it's just that only now they started to take it seriously.) This does go down further on the path of reflection than many others ever achieve over their whole lives. That's because it makes them take their the whole life into account, not only the current stage with its actual painfulness.
We have to distinguish, however, between two main groups in this: one would be those who learn from such an experience that life time is limited, and wasting it for anything that's not of real value is something they will painfully regret. Those in that group have gained a real insight; chances are that they will now reflect much more carefully about their lives and what they're going to do with them. But there's a second group: those who constantly have to remind everybody (whether they want to hear it or not) how badly a pain they had to go through. This is a habit more targeted at exploiting empathy and feelings of pity (or sometimes a kind of boasting with the terrible things you've been through), and needless to say, it's not a helpful way of looking back for anyone. Again, there's a difference between looking at past ordeals as helping you to become a more solid and determined person in your quest for excellence, and taking them as a mere occasion for some yammering. (Add to this that complaining and whinging invariably increases the perceived badness of any pain, because the imagination amplifies exactly what you're fearing. As with any sort of fear, if you try to retreat from it, the badness will follow you; but if you stand up against it, it will ebb back.)
Remember that pain and illness themselves are indifferent — it's not they that make your live good or bad, but your attitude to whatever happens, including pain and illness. (Obviously, if you fail to avoid some preventable pain because of some foolishness, that is bad in a strict sense, but even then it's not the pain itself that is bad, but your foolishness that brought it about.) In this sense, painful experiences in themselves don't make your life better or worse, but pathetic whining makes it bad, while firm endurance makes it good, despite the misfortunes in it. (Some people's unimpressed holding out against severe illness and unfazed pursuit of their goals in spite of it has made them even widely known and admired for it. Enduring illness is an instance of courage.) It's not the amount of pain that counts in the end, for that's not something you can choose: it's rather how you treat it. Take care.
