Imagine a person buys a new house. A REALLY luxurious house. 10 million dollars. Better than anything he ever dreamed of. No mortgage. All paid off. AHHHHHHH!!
How excited is he? Off the charts excited! But wait? How long will he live in this house? He doesn't know for sure. All he knows for sure is one thing - that it is only a temporary dwelling. A דירת עראי if you will [and even if you won't:-)]. Or if you prefer - a "rental". His "lease" might run out today or it might run out in a week or a year or ten years - but nobody lives [in this world] forever. So the house isn't his forever. But that doesn't cast a shadow over his joy. He is darn excited:-)! We don't like to think about the temporal nature of all of our possessions. Like, live and enjoy and don't about that tomorrow when you will die [everyone will die on a certain tomorrow - the only question is when that tomorrow is].
Now, you do a MITZVA. This mitzva will last FOOOORRRREVERRRRRRRR!! How awesome is THAT??? Beyyyyooooondddd awesome!! So why are we so much happier at the prospect of the new house than we are when we do mitzvos?
The pasuk says that there are great punishments because we don't serve Hashem with simcha. This is because we don't APPRECIATE THE VALUE OF A MITZVA. If we would appreciate what we are doing - how very happy we would be!!!
[עפ"י דברי רש"ז מקעלם]
