Aikido principles in theory & applied

O'Sensei admonishes in his book, Budo,'...do not go after many techniques...', but rather,'...strive to learn the principle(s) behind techniques, and one by one make each technique your own' (this isn't an exact quote, but it's accurate in principle, pun intended). We learn techniques to train ourselves in the principles of Aikido, to interact according to those principles[harmoniously], with our environment and the people in it. The techniques, which are specific/"static", are the embodiment of the principles, which are dynamic. This is Takemusu Aikido. We cannot, therefore, learn these principles without training/experience.

What principles do you find most relevant to your training and the training of others, both theoretically and applied?

Principles at work
 

One of the things that I like to use (I think of it as a principle) is the range of effectiveness. One of my favortie quotes of O'Sensei (paraphrasing) is that no matter how strong someone is, once they are outside of their sphere of strength they are weak. I work in Law Enforcement so most of the time the people I have to deal with physically are bigger than me. Even in conversation if you can overextend them you can lead them and talk them out of wanting to fight/argue.
And this is especially true when it comes to physically defending yourself.

principles
 

I know in my own training that you often fail to exhibit a fundamental principle every so often and produce a poor technique (such as extension, centre etc). I don't think I could put one above the other - I like to review what I seem to be lacking at the time. However if there is one thing that puts you off a technique it is trying to concentrate on several things at once. Ideally I hope to practise the principles which I am weak at (and therefore need to be aware of these principles) but a good technique is performed when I have forgotten all about them and it comes naturally. So possibly relaxation/openess could justify as my key principle!

Ian D