Restarting after a longer injury lay off sucks really. Your brain/memory tells you what you could do, but your body tells you you can't. That discrepancy is extremely demotivating. So consciously start it easy and set your training goals real low at first. That way, if you comfortably can achieve those little goals, you get positive feedback to motivate yourself. Increase the goals at a reasonable pace so you stay comfortable. After a few weeks you will have a routine and mindset of training again, then you can lift the training goals at a level where it's getting uncomfortable and you start to have to fight to achieve the goals. At that time you will be in full training and back on track again.