Here is one of our old conversations which you may find helpful to answer your question: http://www.allaboutgod.net/forum/topics/can-we-lose-our-salvation.
The answer you receive depends upon the background of the person you ask. My recommendation is this: serve God with your whole heart, commit everything about your life to Him, seek his wisdom and direction for your life, confess sins as you become aware. Don't take chances and seek purity and the proper fear and respect of God. He is HOLY and commands us to be holy. This isn't easy, but we must seek this daily, and confess mistakes to Him as be become aware. God knows the heart, searches the heart, and convicts us of our failings. Seek and you will find what you need. Salvation is not a game. Best wishes and stay resolute. Annie