You cannot lose your salvation - once you have it. so the only question is whether or not you really have it. We should look for a growing awareness of Christ's presence and power in our life. Then we will know if we are true Christians - changing from the inside out - or just "going through the motions."
If I am truly "saved," then I belong to Christ. I should see Christ-likeness emerging in me. My mind should be more like His. My life should look more and more like His. If it doesn't, then perhaps I need to ask myself what the strength of my commitment to Christ as really been.