When the light on my vacuum cleaner comes on, it means that the filter needs a clean. Lately it has been coming on all the time. We have been doing renovations, which has meant a lot more dust and dirt in the vacuum cleaner. But even when I had just cleaned out the filter the light would come on again. It was starting to frustrate me, so I told my husband. He said, "I think there's another filter inside." So he had a look and found a second filter out of sight that I hadn't known about. He took it out and it was packed with dust and dirt! That was the problem. So I gave it a thorough clean and let it dry for 24 hours. After that it worked good as new again with much more suction.
That inner filter is a picture of our hearts! It's something you can't see from the outside and yet it affects everything. Our hearts can become blocked up with sin. Working to clean up our actions doesn't help, because it's the inside where the problem is. The inside affects the outside. It affects how effective we are as a Christian. We need to stay close to God by prayer and reading His Word to become aware of our sin. Then we need to confess it and forsake it.
David prayed, "Create in me a clean heart, O God; and renew a right spirit within me." Psalm 51:10
Psalm 139:23-24 says "Search me, O God, and know my heart: try me, and know my thoughts: And see if there be any wicked way in me, and lead me in the way everlasting."
Proverbs 4:23 says "Keep thy heart with all diligence; for out of it are the issues of life."