Of course the above follows for individual training as well. Of course we want to nurture ourselves. But who is to say that hard training is not self- nurture? I would argue very much that it is, and of the highest nature. We should distinguish between discomfort, pain, and injury. We should know our limits and push them. We always want to avoid injury, but we need to discern the difference between discomfort and dangerous pain. In many cases what we call pain is our body crying out because of a lack of conditioning. Some discomfort is necessary for growth. In short, we should always, always aim high. If we train the right way with the right attitude, mastery is never an end goal but a part of the process, that is only found in endlessly searching for itself.
The key to training hard is training soft. Stretching, warm-ups, and Qigong are necessary prerequisites for hard training, whether it be lifting weights, vinyasa, sparring, cardio, etc... It is important to engage all the muscle groups, relieve stiffness, engage the energetic body, and warm up before turning up the steam. Accordingly, it is important to do these practices at the end of a hard workout as well. An intelligent cool-down with joint-opening exercises, stretching, and lying Qigong (Shavasana) will go along way and lead to a more holistic conditioning.
Just do it; do it often; but do it intelligently.