Don't be too optimistic at the beginning of your personal training regimen; you won't be able to do a ten-mile run right away. Ease into your training, and work your way up. Before long, you'll be amazed at how far you've come, and your ultimate goals will seem more attainable.
If you can afford it, hire a personal training expert to help you with your program. They know the best things to do and, even better, what NOT to do as you ease into your training. You may ultimately find that your trainer is worth their weight in gold.