The quiet path winds gently uphill through leafy forests and beside a gurgling stream. The birdsong in the trees matches the joy in your heart as you stroll along. Your backpack doesn¿t feel too heavy and you¿re enjoying the pleasant shade from the warm sun. Then you reach a fork in the path. You pause. Should you follow the track which runs alongside the stream? It looks pleasant, a lot like the path you¿ve just been following. Or should you turn to the right? This one is narrower, rougher, and steeper. It leads out of the forest, towards the rocky, grey mountain. Both paths lead uphill, but you know that the mountain one will test you and try you. You will need to climb, to push yourself to your limit. The temperature will fluctuate between extremes of scorching heat and chilling cold. Your backpack will begin to feel like a heavy burden. The gradient may be so steep in places that you will find yourself clinging by your fingernails. But the higher you climb, the purer the air will b