There is a story of two preachers who died and both went to hell. The first preacher told the second preacher "I believe the Bible teaches once saved, always saved. I thought I was saved while I was on earth, yet I am in hell. I must never have been saved to begin with". The second preacher said "I believe the Bible teaches you can lose your salvation. I thought I was saved while I was on earth, yet I am in hell. I must have lost my salvation". This is a pretty ridiculous story, but it has a very good point to it. What is the point?
The point is not "can a person lose their salvation, or not"; the point is that it is most important to "make sure you are right with God". That you will not spend eternity in hell. Examine yourselves, see if you are in the faith!
Some of the scariest Bible verses for "Christians" are found in Matthew 7:21-23
"Not every one that saith unto me, Lord, Lord, shall enter into the kingdom of heaven; but he that doeth the will of my Father which is in heaven.
Many will say to me in that day, Lord, Lord, have we not prophesied in thy name? and in thy name have cast out devils? and in thy name done many wonderful works?
And then will I profess unto them, I never knew you: depart from me, ye that work iniquity."
How is it than that one examines themselves. More importantly, how does one make sure of their salvation? Well your life should be evidence of your salvation, if your life speaks the opposite - there is a definite concern. But, changing your life is not how you make sure of your salvation, you must repent and put your faith in Jesus - the same as a non-Christian. Surrender your life to Christ.
I don't know if anyone reading this is thinking on their life, and finding themselves concerned; but if you are - don't put it off. You are not guaranteed another day. Humble yourself, make peace with God today.