For an exothermic chemical process occurring in two steps as follows 
$\left(i\right) A+B\to X \left(slow\right) \left(ii\right) X\to AB \left(fast\right)$
The progress of reaction can be best described by :     

First step is slow (require more activation energy) second step is fast (less activation energy) and overall reaction exothermic, so product energy level should be less as compared to reactants.