How can I know if I'm operating in faith?

Both faith and fear represent some form of belief. Faith is a positive belief and fear is a negative belief. They are opposite to each other. You cannot operate with both positive belief (faith) and negative belief (worry, doubt and fear) and expect to receive results.

James 1:6 NIV
6But when he asks, he must believe and not doubt, because he who doubts is like a wave of the sea, blown and tossed by the wind. 7That man should not think he will receive anything from the Lord;

Godly faith is believing something that moves you closer into God’s will, namely – the promises of God. Fear is believing something that moves you further away from God’s will. Therefore, fear is believing something that contradicts God’s will, something that contradicts one of God’s promises.

The tell-tale sign to know if you’re operating in faith is to ask yourself, am I operating and making decisions out of fear? If fear is present, then faith has diminished. Fear has two very close friends – worry and doubt. Worry, doubt and fear – they are all interrelated. If you can recognize when worry, doubt or fear are operating in your life, you will know the area where your faith needs to be strengthened.