Have it ever occurred to you that 30% profit is NOT magnitude-wise the same as 30% lost ?
When your $100 investment earns a 30% profit, it goes up to $130 = 100 x 1.3. Pretty straight forward, no problem there. Then it makes a 30% lost. Instead of going back to $100, it actually drops to $91.
130 x ( 1 - 0.3 ) = 91
The calculation above is not deceiving. A 30% discount on any market item is actually calculated the same way.
So you have just made a lost of $9 !
Sounds tricky ? Lets see what if it moves the other way round.
This time you lost 30% from your $100 investment, it become $70 = 100 x ( 1 - 0.3 ). No problem here. Then it earns back 30%. This time you got 70 x 1.3 = $91. Again you lost $9 !!
There you go, sometimes 30% earning is NOT necessary the same as 30% loses. Get your numbers right in both your business and investment, 9% strategical lost due to a not-so-well-setup strategy could be killing.