In Parasha / Torah Reading Ki tavo, in the first aliya – (Devarim / Deut. 26:11) we read “And you shall rejoice for all the good that G-d gave you, your household and the Levi and the convert who is among you. ” Why do we have a commandment to be happy for the good we receive? It is natural to be happy for good.
One reason is many have the attitude of ‘It’s my right.. I deserve it” Thus when they do receive good, they are not so appreciative. G-d is telling us to have the attitude that everything we receive is not a given. It is a gift from G-d. If we think thus, we will not take things for granted and be happy and thankful to Hashem for each thing we receive.
Having appreciation to G.d leads us to a more fulfilling life. Thus we say the blessing of Shehechiyanu (Blessed are You, Our G-d … that He made us live, established us and that allowed us to arrived to this time.) on Jewish holidays to appreciate our arriving in good health to this time.