Is my heart pure (Mark 7:20-23 )

Is my heart pure? What am I doing to maintain it, to feed it so that it is pure and my thoughts are pure?

Mark 7:20-23 (http://www.biblegateway.com)

New International Version (NIV)

²⁰ He went on: “What comes out of a person is what defiles them. ²¹ For it is from within, out of a person’s heart, that evil thoughts come—sexual immorality, theft, murder, ²² adultery, greed, malice, deceit, lewdness, envy, slander, arrogance and folly. ²³ All these evils come from inside and defile a person.”