The Medrash Tehillim ( Mizmor 146) expounds on the topic of bitachon on the verse (Tehillim 146:4): “His wind leaves, he returns to his soil.” It relates a moshol of a balloon filled with air that is sitting on the ground. If someone sees it, it may look big and frightening, but if he lets the air out, he sees that it is nothing special. The man will then say, “Is this what I was afraid of? It’s just a bunch of air!”
The Medrash continues: “Do you want a defender that will last forever? Trust in Him at all times, and you will survive! This is as is stated (Tehillim 146:5): ‘Praiseworthy is he in whose help is the G-d of Yaakov.’ …If one trusts in Him, his reward will never cease.”