During my career in the Royal Marines we had to be fit for any event around the world with less then 24 hours notice to move. Being a Commando you would never know in advance what is going to confront you when you arrive for battle. So you had to be prepared for any hardship and anything that could be physically demanding.
The components of fitness as I see it are:
Spread the Stress
One thing you'll notice with the type of cross training that comes with covering all these components is that all of the body's joints and muscle groups are used in many various ways of movement and with various levels of intensity. Training this way will generally spread the physical stress of training across all your joints and muscle groups creating balance. When applying various training methods to your training programme you'll also be promoting injury free training.
Of course if you're training for a particular event then training will have to be adapted and focused but then resuming a regular balanced approach to your fitness training when possible.
For injury proof training and for 'Total Fitness' try to include all of the components of fitness in to your training programme.