One of them is the simple act of washing Netilas Yodayim before eating bread.
This Halocha came about when the Beis Hamikdosh still stood. Before eating Terumah, a Kohen would need to wash their hands so that they would be pure. This requirement was applied to Chulin (non-sacred foods) and was extended to Yisraelim as well as Kohanim.
Even now when Kohanim no longer eat Terumah, we are all still required to wash our hands before eating bread. The reason for this is that Chaza”l anticipate that the Beis Hamikdosh will speedily be rebuilt and we will have to be immediately familiar with observing the laws of purity and impurity.
The return from Golus Bavel was not a complete Geulah because they did not make a remembrance for Yerushalayim and the Beis Hamikdosh. In the merit of our Zecher LeMikdosh we will merit a Geulah Shleimah (Chasam Sofer).
Next time you wash Netilas Yodayim, take a few moments to meditate on how this act is preparing ourselves and the world for the imminent coming of Moshiach and the Beis Hamikdosh Hashlishi.