No! Thoughts cannot cancel God’s promises at all—even those placed in your heart. The promises of God are received by the force of faith that comes out of the heart, not the head. Therefore, it is possible to believe in the heart and have doubt in the head and still obtain God’s blessing.
That said, negative thoughts can become a problem—and a big one. If you continually allow negative thoughts to remain in your mind while using your faith to believe God, those thoughts will drop from your head into your heart. Eventually you will speak those negative thoughts from the abundance of your heart. Once you speak those thoughts in words and they register upon your heart, that’s when they will control your life.
Similarly, unbelief from another person will not hinder your faith from working. Romans 3:3-4 says, “True, some of them were unfaithful; but just because they were unfaithful, does that mean God will be unfaithful? Of course not! Even if everyone else is a liar, God is true. As the Scriptures say about him, ‘You will be proved right in what you say, and you will win your case in court.’” It does not matter what anyone says when you are established in what is yours from God’s Word. You can receive God’s blessing in any environment.
When others’ voices rise up to judge you, you will prove them to be wrong (Isaiah 54:17) by knowing what is yours in Christ Jesus and standing your ground. Words can be intended as weapons against you, but they cannot prosper unless you receive them (2 Corinthians 10:4-5).