How does understanding that characteristic of our Heavenly Father give us comfort? Because we can depend on someone who never changes. We can trust someone who is the same yesterday, today, and tomorrow. We can believe with all our hearts in someone who will never go back on his word.
God tells us over and over again in His Word that He loves His children. That His love is everlasting. That nothing can separate us from it. He not only will not stop loving us, He can not stop loving us.
In a world of instability--where love can be pulled out from under us at any time and for any reason, where people close to us cannot be trusted, where sometimes even our own fathers forsake us--it's reassuring to know that our Heavenly Father is always the same. He loves us and nothing will ever change that.