I think you first need to be congratulated on listening to your body and doing what it was asking of you. Pulling out of a race, especially one that we have trained so long and hard for, is NEVER an easy decision. Sometimes we can think our bodies are ready and able to hold up to the miles and miles we put them through during a marathon and marathon training, but then race day rolls around and things just do not go as planned. You should be really proud of yourself. Not only did you probably save yourself from getting injured further (had you kept running), but you made the tough decision to put your health before your running. There is always next year, and there will always be another race to sign up and run!

As far as runner burn out... well, that is definitely a real thing too! You could choose to push yourself to signing up for another race and endure months and weeks of intense training to prepare yourself. But honestly? That probably is not a good idea, and here is why. Often times, mental fatigue and burn out is our body's subconscious way of telling us it needs a break. It just needs some time away. This is especially true when we have pushed it to its limits, and it is facing a possible injury (which, it sounds like might be the case for you). Sometimes, in order to come back and run as strong and fast as we possibly can, we need to give ourselves a break. And however long that is, is different for everyone. Some people need just a week off before they jump back into training for another marathon. For others, their bodies needs longer to rest. And so does their brain! The mental game of pushing through tough workout after tough workout, the discipline of running in the dark, in the cold or hot, or in extreme circumstance just to get your run in is exhausting. So is having to be on top of your nutrition 24/7. (It ain't always fun to have to pass up birthday cake and ice cream at every single office party, or go home instead of going to happy hour with friends!)

To really re-find your motivation, it sounds like you need TIME. And give it to yourself! Be patient with yourself. Be encouraging and supportive. Maybe you need to turn to some other forms of exercise, or even just gentle movement like yoga, in order to give yourself rest and motivation to get back to running (eventually). You might find some real joy in exploring different ways to be active and move your body. With adequate rest (mental AND physical), you will likely find yourself starting to have the 'itch' to get back out there and run. But for now, rest and explore other areas of fitness.