Light Relief is especially for you if you have accrued an excessive amount of work or other commitments, and it is close to pushing you beyond your ability to cope. You have probably been in this situation for a while and keep trying to get on top of it all. You have long passed the point where you should have stepped back from it all and allowed yourself to rest and replenish. Light Relief “pulls the plug” on the drive we use to override our exhaustion. So one then goes pretty much straight away into the fatigue level as it really is, and the best thing at that point is a nap.
By way of contrast, Double Espresso is a combination specifically aimed at doing the opposite, helping one to push on and override fatigue briefly.
In simple terms, Immediate Relief is for acute stress (emergency situations etc.), whereas Light Relief is especially for those suffering from long term stress.