In Matthew 6:24, Jesus said to his disciples and the crowds, "No one can serve two masters. You cannot serve God and mammon." Of course, God we must serve, so "mammon" may be replaced with someone or something else. What comes to my mind is that "we cannot serve God and ourselves." If we serve ourselves first, we cannot possibly love God. Even if we place ourselves in second place, we won't be able to serve God whole-heartedly. That leaves us the conclusion that "we must forget about ourselves and serve God only." This is the key to freedom and holiness! And our reward will surely be great in heaven!