The bond energy is defined as equal to the amount of energy given out when the bond is made (or absorbed when that the bond is broken).
So when a bond is made, and the system cools to its original energy, the amount of energy given out, -DeltaH, is more or less equal to the bond energy.
Noticed that minus sign. For a process that releases heat, DeltaH is negative.
Internet to the rescue
Hope this helps!
