I don't know where I found this but I have it written down in my commonplace book. I hope it will be an encouragement to you.
To squander the grace of God, that is meant for the real trials of today, upon the mirage of impending trouble that might happen tomorrow is foolish, and betrays a wrong perspective. God is sovereign, we are not, and thus, we have no business seeking to do His job by worrying about what might come our way. The best way to prepare for what might come tomorrow is to faithfully fulfill our obligations towards Him today. Even if tomorrow does bring a trial our way, as it very well may, we can still rest assured that tomorrow morning, just like every other morning, the grace of God will be sufficient to meet that new challenge, for it is from Him. As Jeremiah proclaims, "[His mercies] are new every morning, great is Your faithfulness!" (Lam. 3:23). The distracted man worries, but the wise man makes his plans and forms his strategy with the object of impacting eternity. The future is securely in the hands of Almighty God and cannot be changed. Armed with that knowledge, we must find our reward in the eternal rather than distractedly scrambling after the temporal. Stop worrying, and start serving your Master from an undivided heart!