So much of how we handle life depends on the choices we make as they relate to our thoughts and attitudes. For instance, a good friend of mine has a saying: " have a wonderful day unless you've made other plans." We have total control over what we choose to focus upon. The process of protecting our heart begins with having control over our thoughts.
Do not let your hearts be troubled. Trust in God; and also trust in me.
In the Scripture we see two simple choices that we are instructed to take which will help us walk in faith. One is the choice to not be troubled. The other is the choice to trust God. If we can do these two things, God will meet us in the place of faith and our spiritual heart will be protected from depressing thoughts which lead to despair, gloom and disappointments.