What you believe can change your circumstances.    To believe is the verb form of faith.  The definition of faith is being sure of the things we hope for and knowing that something is real even if we do not see it (Hebrews 11:1).  So in that sense, the word believe is accepting something is true, trusting in what you think.

The opposite of faith/belief is doubt, or unbelief. We stand strong in Christ by faith (see II Corinthians 1:24); however, the reverse is also true: we fall away from Christ through unbelief. “Wherefore let him that thinketh he standeth take heed lest he fall“ (I Corinthians 10:12).

2 Timothy 3:16 says, “All scripture [is] given by inspiration of God, and [is] profitable (beneficial) for doctrine (ideas or beliefs), for reproof (blame), for correction, for instruction in righteousness:”

If God’s word says it, believe it!