On Monday, Fitsugar posted tips for breaking up with your personal trainer. From personal experience I can tell you it is probably just as hard as ending a friendship. Since I started working out with trainers a four years ago, I have had four different trainers. Two of which I "broke up with."
The first one wasn't that difficult. I had been thinking about testing out using a trainer for some time and was paired up with Bruce 
through the gym. He was a great starter trainer and helped me figure out what I wanted and didn't want (we did 30 minute sessions twice a week and I felt like he talked a lot and didn't have me do things that I couldn't do on my own). So when my first set of sessions were complete, I said thank you and moved on without him.
Then came the wedding, and I wanted to start training again. Heyward was a trainer I had seen around the gym regularly. He always said hello and his clients seemed incredibly satisfied. So, I signed up and it was probably love at first training. Not only did he do morning sessions, but he also did hour-long sessions. After my first session with him (I went in thinking it was 30 minutes), I thought how can I be THIS out of shape. Over the next 8 months Heyward introduced me to TRX, kettlebells, and some serious weight lifting. I loved every minute of it and when I had to move from NYC to DC, I actually begged him to come with me. (He didn't, but he sent me every routine he had created for me via email so that I could continue my training.)
Joining a new gym in the height of wedding training was nerve wracking. Based on my training style I was introduced to Scott. He trained me hard for the wedding and I was incredibly happy with how I turned out. A few months after the wedding, I decided to go back to training, and for some reason it just wasn't working. This was the hardest break-up ever. I wrestled with it for a few weeks. Had a private meeting with a trainer friend, and then finally took a deep breath and spoke with the person in charge of trainers--I couldn't even speak to him about it. It was really hard, I practically avoided the gym thinking Scott would be there...but it had to happen.
Now, I am with Leslie Ann (my trainer friend) and it has re-energized my love of training, because I can actually see results. Leslie Ann really seems to understand what my body needs; a combination of strength & agility training...alternating body weight with heavy weights. I've dropped 2.5% percentage points in body fat and feel better physically.
The thing I have learned about working with trainers is that you have to speak up, and let them know what you want. You shell out significant money for them and they have to work hard to give you the EXACT results you want (well you have to work hard together).