I can honestly say that whether it is gaining muscle or losing weight visualizing the result works. It keeps your attitude up and gives you a better over all well being. Having an attitude where you give yourself no hope is deffinatly not helping you out.
Granted I don't know you what so ever and you could have started your journey at 600 lbs but with the correct diet (which your doing), exercise, a positive attitude and time you can get to whatever your goal weight is. You may get their and have saggy skin or whatever but that is cosmetic and can be fixed if need be. Don't sell yourself short.