How do you view Christianity? Is it a battle, a race, a religion, a set of values, an organization, or a calling? When you think of your faith, what is one word that could sum up the whole idea? You could have responded with any of the above, but I would submit to you that the best word to use to describe Christianity is relationship.
Our Christian life is not about following rules, obeying commands, identifying with a culture or society as much as it is about forming a relationship with God. Christ says that the greatest commandment is "Thou shalt love the Lord thy God with all thy heart, and with all thy soul, and with all thy mind," Matthew 22:37. God wants us to have a relationship with Him. He wants us to desire Him above all else.
Think about Psalm 23. The psalmist talks of His Savior. He tells us about how much God has done for him and continues to do. That is where the joy of Christianity comes from. If we live without ever experiencing the love of God, we never truly live. If you try to live for God, without ever knowing him, you will not succeed.
I would like to encourage you as other times. Get to know the God that you serve. If you struggle with working up the motivation to serve God, you probably have forgotten who you are serving. Ask God to remind you of His love. Ask God to change you, and spend some time in His Word. If you do, the Lord will transform you. The Christian life is not about forcing yourself to serve God, its about being transformed into someone who naturally wants to. I challenge you, get to know your Savior and ask Him to motivate and teach you to serve Him.
"For it is God which worketh in you both to will and to do of His good pleasure." – Philippians 2:13