{Give all your worries and cares to God, for He cares about what happens to you. 1 Peter 5:7}
To borrow a quote from a friend, "doubt is just faith in something other than God".
"Faith reminds itself of what the Scripture calls 'the exceeding great and precious promises' says Lloyd Jones. "Faith says: 'I cannot believe that He who has brought me so far is going to let me down at this point. It is impossible, it would be inconsistent with the character of God.' So faith, having refused to be controlled by circumstances [or feelings!], reminds itself of what it believes and what it knows." (taken from this inspiring blog)