Keep and guard your heart with all vigilance and above all that you guard, for out of it flow the springs of life. (Proverbs 4:23 AMP)
Be careful how you think; your life is shaped by your thoughts. (Proverbs 4:23 GNB)
For the thing that I fear comes upon me, and what I dread befalls me. (Job 3:25 ESV)- self fulfilling prophecy
Not everthing that you feel or think is true! However, your thoughts shape your life! If you think a thought long enough you become it and act it out!
If you want to change your life start thinking like Jesus about every aspect of your life! Find out what God says about your challenges and think about that!