Correct Breathing method helps !
Never breath too heavily while running . Heavy breath-in only makes
u more fatigue .
Only do heavy breath-in once in a while , how to say ? Meaning
breath hard only once say like .... 500 metres ?
Drink lots of water 2 hr before the run , while running , swallow
your saliva bits by bits .... when necessary swallow a little bit
more , not too much .
While running , find yourself a target , any target , to achieve it
, achieve liao , find another target , and so on and on .... until
you get that 2.4km .
while running , think of something else , not think only about
running , day-dream running is good . 
You'll
never know u have reached your 2.4km .
