1. What you digest changes. You listen and watch more worldly things which will cause you to become slack in conviction and standards you may have once cherished.
2. Church becomes a struggle. If not going to church was never negotiable and now you find that you have to talk yourself into going.
3. Ministry becomes work. A ministry you once was passionate about becomes a burden.
4. Old habits resurface. You may have been delivered from something when you were first saved such as alcohol, drugs, nicotine and recently you find the cravings coming back.
5. Increased Anger or Depression. Being on the fence for God makes life uncomfortable. When you're not fulfilling your purpose, anger and depression can begin to dominate your thoughts and actions.
These are just some warning signs to look for. Unfortunately it's easier to recognize the warning signs then it is to get back on track. Don't try to reignite the fire on your own. It's so hard to escape the control our thoughts can have over our minds. Find a friend, Pastor or someone you can trust to confide in. Address it with urgency because once you recognize the signs of being lukewarm, it generally means you're not far from falling away completely from God. Don't risk your eternity by entertaining lukewarm waters.
Here I Am! I stand at the door and knock. If anyone hears My voice and opens the door, I will come in and eat with him, and he with Me. — Revelation 3:20