There is never a moment when trusting the Lord is vain. There is never a situation, big or small, where you would be better off trusting in someone or something else. He is with us at all times, He is faithful at all times, He is good at all times. Therefore, let us trust in Him at all times.
Lest we be discouraged, He is not unaware that there will come times when our trust in Him is not perfect, or strong. He has told us that it is faith even as tiny as a mustard side that moves mountains.
So let us hold fast the confession of our hope without wavering, for He who promised is faithful; faithful, even when we are faithless.