The worst sin would be breaking the most important of all commandments in the Bible.

Matthew 22:36-37 Teacher, which is the great commandment in the Law?” And He said to him, “ ‘You shall love the Lord your God with all your heart, and with all your soul, and with all your mind.

If you are married there are two ways you can stop loving your spouse. The first is through neglect of communication and time together you simply drift away and get lukewarm in the strength of your relationship, and after a time both would agree that their love is dead. The second is by betraying your husband or wife by having an affair with another person, you commit adultery, and love has been killed. It can be resurrected in both cases, but takes work by both husband and wife.

Our love for God would grow cold in the same way. We begin to have a substitute for God in our life, and commit spiritual adultery, breaking the first of the Ten Commandments by having another god in our life. The substitute for God would be money, cars, houses, cloths, golf clubs, boats, vacations, hobbies. All of those things are legitimate and good under control. How can you tell if you have moved to having an affair with the world? You don’t make time to read the Bible every day, your time in the world leaves little time for prayer, and you use the phrase, “I don’t have time,” every time you are asked to attend any event at the church or to help in some ministry. Because we live in the middle of the world, the world system and everyone around us is loving the world it is very easy to drift away from God and begin loving the world, and it is difficult to see it happening.

1 John 2:15 Do not love the world nor the things in the world. If anyone loves the world, the love of the Father is not in him.

James 4:4-5 You adulteresses, do you not know that friendship with the world is hostility toward God? Therefore whoever wishes to be a friend of the world makes himself an enemy of God. Or do you think that the Scripture speaks to no purpose: “He jealously desires the Spirit which He has made to dwell in us”?

The key thing is read your Bible everyday, everyday, everyday. When you stop, it is because you are entangled in the world and have lost your desire for intimacy with God and you don’t have any time to do the spiritual disciplines that keep your relationship with God hot.

Revelation 2:4-5 But I have this against you, that you have left your first love. Therefore remember from where you have fallen, and repent and do the deeds you did at first; or else I am coming to you and will remove your lampstand out of its place—unless you repent.