The foundation guiding principle of t'ai chi is relaxation. You can try to relax to a certain extent by focusing on the physical body and letting go of the holding you experience in the muscles and this is very beneficial. Yet, it is helpful to realise that to 'try' to relax at all will keep some tension in the mind. Ultimately you cannot try to relax because even that effort will prevent deep experiences. If you have the idea to seek relaxation it will create the unconscious belief that relaxation is something 'out there' that you need to reach out for. So, even at the beginning you are separated from the very thing you desire and you have to strive to somehow acquire it.
In contrast, deep relaxation can come from accepting where you are and allowing the feeling of no effort to come forward. In one sense you can relax your effort to relax. The state of mind that is relaxed is not contrived or invented. It has no technique or method except to let go of any effort or holding on to how you think things should be. The mind is able to expand and release and become spacious. With these ideas in mind, set aside some time to allow your mind to relax. Deep experiences of relaxing your mind will make it much easier to let go of your body and activate the ch'i in your form practice.
Relaxed states of body and mind can become more familiar if you consciously practise just relaxation without anything else going on. You can think of this practice as meditation.
At the beginning it is important to improve your concentration and your ability to focus your awareness otherwise when you think to allow your mind to relax you will not be able to connect. The thoughts will be too busy with too much activity and you will not find it so easy to be able to let go of them. The mind is like a muscle in the sense that if you exercise it regularly it will become stronger.
Sit comfortably on a chair with your back straight and away from any support. Make sure that your feet are flat on the ground. Begin by letting the body settle. Let the force of gravity come to your awareness as you recognise where you resist its effects. Let go and follow the downward sensation, releasing even the slightest tension in the muscles. At the same time keep your skeletal structure upright.
First calm the mind by becoming aware of your breathing. Half close your eyes and put your attention to the nostrils and be aware of the sensation of air. Recognise the in breath and the out breath but don't interfere with the natural rhythm as you continue breathing. It is almost as if your awareness sneaks up on your breathing. Then begin to recognise the gap between the in breath and the out breath. Place your awareness repeatedly, recognising consciously these different parts. Begin to count each complete cycle of breath. If your mind wanders bring it back gently and restart your count. If you can reach seven or fourteen cycles without your mind wandering then relax your mind. Let go of the breath and allow your awareness to become open and spacious.
At first you can make some sort of effort to create the sense of spaciousness and remember not to follow any thoughts that come to your mind. If your mind wanders easily and follows your thoughts without you noticing, then return to counting the cycles of breath. Keep these sessions very short - no longer than ten minutes at a time. If you want to continue for longer take a break after ten minutes and then, after a two minutes break, begin again. If you sit in this way regularly you will learn to meditate naturally without effort. Your mind will become more open and yet at the same time concentrated.
When the mind is relaxed; it is not 'doing' it is being in its natural state. When thoughts and perceptions come just let them pass by and leave your mind in its natural relaxed state.