William Burkitt on Matthew 6:34

Here our Saviour re-inforces his exhortation from solicitous care for worldly things, assuring us, that every day will bring with it a sufficient burden of trouble, and therefore we ought not to torment ourselves, by antedating our own sorrows, and foretelling what may or may not come to pass.

Learn, That it is a painful sinful and unprofitable evil, to perplex ourselves with distrustful and distracting fears of what may come upon us: every day has its own duty and difficulty; and though sufferings must be expected and prepared for, yet we must not torment ourselves to-day with fears of what may be tomorrow; but every day cast our burden of care upon that God who daily careth for us.