Pre approval

We talked to a buyers agent yesterday and had I guess what you would call an orientation for new home buyers. He just basically told us where to start, what all to do, and went over all the steps etc. The first step of course is to get pre approved. We are going thru the VA obviously, which is supposedly the best but I am still worried that we wont get approved for anything! Is that possible? We know what we can afford per month, but Im just worried they will say "oh, we dont want to give you a loan." Mark has really been working on getting his credit up, and its in the excellent category now, so I am just wondering how hard it is to get approved. I go to bed every night dreaming of getting a house literally! Anyone have experience with the process and know what our odds of getting turned down are?