Matt,
 
I think you may be confusing salvation of the spirit ( a free gift paid for when Jesus layed down his life on  the cross) and salvation of the soul which a believer must work out on his own by living his life for Christ. Salvation of the soul is optional but highly recommended.
Here are some links explaining the difference between body, spirit and soul. This is an in depth subject not easily answered in a short post.
 
http://lampbroadcast.org/Books/SOS.pdf
http://www.raptureready.com/resource/wilson/w8.htm
http://www.thefirstfruits.org/salvatn/parish.htm
 
Steve