Emax

Try and assign the sample so you can trigger it on very low /slow keys, it 
can sometimes help to find a good loop point.
  or / and use the crossfade function. # use the autofind looppoints. or 
use very short loop.
or Copy the sample, with your best loop, Cut out the portion before the 
loop sets in, reverse it the sample, now splice this one with the original, 
which you may have copied too to avoid destroying your original. set the 
loop start point as in the original and the end point at the end of the 
reversed, spliced portion,  now you have an alternate forward reverse loop, 
which sometimes is easier to loop.

But sometimes it is just impossible to make a Really good loop.