Stress is a result of either fear, worry or doubt or a combination of two or more of these.  It is a fear you will not obtain something you desire or will have something happen you do not desire.

It is really a lack of trust in God's Love for you and control of your circumstances.

It is Satan trying to have you doubt God's Love and Control.

This is why we are told:

1Pe 5:7  Casting all your care upon him; for he careth for you.

Jas 4:7  Submit yourselves therefore to God. Resist the devil, and he will flee from you.

Rom 8:28  And we know that all things work together for good to them that love God, to them who are the called according to his purpose.

Doing these things will give you peace and if you lose it then fight Satan who is trying to take away your peace. (The Five Steps helps with this)