Proverbs 4:23—Above   all else, guard your heart, for it is the wellspring of life. 
This morning, as per   my custom, I placed a tea bag of green tea into a plastic mug, and poured   over it boiling water. The cup is equipped with a black top to reduce the   chance of me spilling. I don’t want tea decorating the papers strewn across   my desk, nor do I need tea-stained clothing. 
Suppose a small crack   developed in my mug. It would be annoying wouldn’t it—to contend with a cup   that leaked? If holes appeared, I would either have to plug them somehow or   throw the mug away. 
When I choose to   follow Jesus, my intent is that He should have my whole mug—my heart. When He   fills me with His Holy Spirit and teaches me through His word, His desire is   that I am holy as He is holy. For my heart to function as God intended, I   must obey His will!
To give my heart to   anything that is contrary to God’s will, is like   puncturing my mug. The more leaks I spring from selfish desires and ungodly   behavior, the less able and willing God is to fill me with Himself. How can I   know or serve God if He cannot entrust Himself to me? 
God said about the   Israelites Moses led out of 
Give me an undivided   heart O Lord! Don’t let the cravings of my flesh turn my core into a leaking   vessel of shame! Create in me a wholehearted love for You that gives off the   aroma of a joyful attitude and blesses Your palate with the rich taste of   godliness that comes from obedient service and a humble spirit. Fill my cup   Lord, for Your glory.
Inspiration
The knowledge and   vision of God is dependent entirely on a pure heart. Character determines the   revelation of God to the individual. "Blessed are the pure in heart, for   they shall see God."—Oswald Chambers in Biblical Ethics