Our Scripture reading today is John 15:9-11.
Verse 10, "If ye keep my commandments, ye shall abide in my love; even as I have kept my Father's commandments, and abide in his love."
How does someone really know that we love God?  Can mankind see within our heart?  We know that is not possible.  1 Samuel 16:7, "But the LORD said unto Samuel, Look not on his countenance, or on the height of his stature; because I have refused him: for the LORD seeth not as man seeth; for man looketh on the outward appearance, but the LORD looketh on the heart."  
If we love God, it will show in how we obey His Word.  Our love for Him is birthed out of our obediece to Him.  A love for God will lead me to live my life to bring Him honour and glory.  I will want to do whatever He leads me to do.  My attitude will be, "I get to tithe and give offerings, I get to be an ambassador for Jesus Christ, and I get to love my enemies."  A true disciple of Jesus Christ will honour God's Word.  This takes place when we obey from a heart of love.