When practicing with your partner, keep in mind that Aikido is the way of harmony of energy (spirit). That means you should always aim at joining with your partner's energy when you lead and direct your partner as well as when it is your turn to follow your partner's lead. Do not resist your partner unduly, thus breaking their flow of ki. It is very frustrating to learn under such circumstances, and it does neither of you any good. Especially beginning students have to go through the motions many times before they can get a feeling for the flow of ki, and it is of no use to stop that process through resisting. On the other hand, you should avoid anticipating your partner's motion. Just follow their lead. This is almost as difficult as leading yourself, and very good practice in itself.
When it is your turn to be thrown, make sure that your attack is committed and a serious one because it is difficult and also senseless to apply a defense technique against a half-hearted, lukewarm attack. You are not supposed to hurt your partner, but you have to put your mind, i.e. ki, into the attack. In general, it can be said that the harder the attack, the harder the fall will be. Therefore you should adjust the force of your attack to your ability to take ukemi (the fall).
All of this is necessary to practice in harmony. Avoid talking. Aikido is movement.
Ukemi is not falling on your own. You must follow nage until you fall naturally. By this, you can understand the formless form of ki-movements. This understanding allows you to develop kokyunage from basic forms after appropriate training.
Y. Kawahara
The utmost hardness of practicing can be attained within the individual's attitude and exercising kokyu-power, which is completely different from practicing roughly or exerting physical strength, disregarding the partner's ability and strength. Strictness in Aikido training must be found in the sincere and harmonious atmosphere where all the participants practice with each other caringly and sensitively. Leave your egocentric and egotistic attachments behind before entering the dojo.
As you practice, always pay attention to your posture. Keep your center down. It is a commonly found tendency that as a student becomes more experienced and more skillful than many other students, he forgets the importance of lowering his center. The better you become, the lower your center should be, thus the more respectful to others you become.
Take a proper ma-ai. This is the key to appropraite movements.
Make ki-ai (vocalization) whenever appropriate. Ki-ai is an expression of your dynamic life energy.
In shomen-uchi especially, nage initiates the movement. Both nage's and uke's hands come from the very center.
F. I. Ishiyama