Basic question of our existence: how can we have a relationship with His essence? Hashem tied the Jewish People to Him with a bris. Hashem brought us up to Him and He brought Himself down to us. Tu B'Shvat custom to eat fruits of the Land of Israel. When a Jew keeps a custom it is "dessert after a meal" since we want to give nachas (joy) to Hashem. On Tu B'Shvat we are looking for excitement in our Yiddishkeit beyond our responsibilities. We are learning to reach Hashem- the Infinite.