I think setting long and short term goals is a good idea. However, I think we have to develop the thinking that even if I don't reach my goal, I have made progress. Many times fitness and weight loss efforts fail because we become so focused on the ultimate numbers - "I have to reach my goal". For me, in the past, if I wasn't able to reach short-term goals, I was very discouraged from continuing to the end.
Sarah Ann, I too find visualization difficult. I have read that learning to meditate or slow down your mind helps with this. I however, have not developed the discipline for meditation (I always fall asleep - my sister refuses to take me to her classes again). I am finding that focus for me has to be a deliberate mental act. I have to mentally make myself focus while working out. This means that now, when it's time to workout I refuse to let any of the things that pop into my thoughts stay there. I try to focus on my breathing and exercise form (in the past, I would just go through the motions).
When it comes to "what's next", I think each person has to go with what they know has worked for them. If I achieve my weight loss goal, I'm going to continue to do the things that got me there. There are always going to be studies that promote different ways of eating or working out - why risk what works?