Can We Lose Our Salvation?

Can a true believer ever lose his salvation by sinning, ceasing to believe, or in any other way?  If you can lose your salvation, can you be saved twice or more?  i.e. if you are made a new creation, saved from the dead, transferred to the kingdom of light, adopted into the family of God… are you able to leave, give this up, and be reborn a second or third time?