I wrote this in reply to a runner that had been struggling with injury and now dealing with fear of re-injury limiting her. I thought I'd share it with you to generate some thought and discussion. We all struggle with fear and injury.....
Fear is normal....embrace it, it is supposed to be there when you are stepping out of your comfort zone. I have had intermittent trouble with IT pain and plantar fasciitis and have still been able to accomplish some amazing things over the past 3 years including 3 100 mile finishes...one first female ;)
I say that to say your goals are more than possible, despite some painful experiences you have had. We all have aches and pains to work through...some physical, some mental. Don't stop because it hurts...evaluate the hurt and work on the root cause to begin to ease/eliminate the pain. Some pain can be worked through while continuing to train, obviously, some require stopping and resting...same is true with our minds. I have managed to train through a lot of my IT and heel pain and have made great strides in working to resolve some of the factors that have contributed (mostly form and strength issues). I have also had to stop training for brief periods to rest those "hot" areas.
I have learned it is a work in progress and seeing it as such has eliminated a great deal of frustration. I see my body kinda like a mechanic sees a car. If you take your car to the shop because something is rattling, the mechanic is going to tinker with it, using his knowledge and experience. If what he does fixes it, great! If not, he tinkers with it more until it runs properly. I also see a lot of runners stop running because of injury or aches/pains, advised by their medical professional "your should stop running, running is too hard on your body". Again, like a mechanic, if you take your car in because it is rattling, he's not going to say, "you should stop driving, driving is too hard on your car". He's going to work to help it run better and more efficiently and he's going to help you work out the rattle.