I've been studying Yang style Tai Ji, Qi Gong, Cha Quan and Xingyi Liuhe for seven years. All are "internal" martial arts, aimed at balancing and strengthening "qi" energy. My tai chi master (we call him "sifu") says this:
"Taiji is Dao.
Taiji strengthens your muscles and ligaments, harmonises your qi and your blood, cultivates physical and mental health, eliminates disease and prolongs life. All can achieve benefits from practicing taiji as a method of health preservation, irrespective of innate ability. When practised correctly, taiji is an exercise that results in pure benefit to the practitioner and rarely results in harm.
Taiji follows the theory of 'dong' (movement) and 'jing' (stillness). The application of this theory requires an understanding of the transition between emptiness and fullness. Taiji is practised with with an upright, centered posture, which creates mental stillness and relieves physical burden. Movement in taiji is light, nimble and always circular. Attention during practice should be focused on internal movement, and taiji is therefore considered an 'internal martial art'. All movements in taiji are very natural and relaxed. Because of this it is suitable for practitioners of all backgrounds, including the elderly, the young, male or female. It is also suitable for physically handicapped people and can be easily adapted to suit anyone's needs.
To achieve the greatest benefits from taiji, daily practice is essential. The idea of active training, where you are aware of the intricacies of each movement as it is performed, is especially important. Every single movement should be studied until it is understood in great detail, which serves to enhance awareness and control over your internal landscape. The benefits of taiji are physical and mental, and will add a broad perspective to your personal wisdom.
Regular training of the taiji form is at the heart of taiji practice. The form provides the framework for all movements, and through practice it is continually refined, resulting in great benefit to the practitioner. Kneading hands ('push hands') is used to train martial application and reinforce the understanding of Yin and Yang and how its change benefits health and wellbeing.
If you persist with your training, it will eventually guide you to the right path in life. You will have a strong feeling of qi permeating every part of your body, and through practice you will equip yourself with heightened sensitivity, enhanced reflexes, and a greater understanding of energy. Continued practice will give you insight into the ideal of ultimate relaxation and you will eventually be able to apply this in all aspects of your life. Given time, you will reach a level where you perfectly understand your relationship with nature."
Most Tai Ji styles would bring benefits to the practitioner but it's important to find a teacher that you like and whose teaching style suits you. My teacher has a strong spiritual and philososphical approach to his teaching. A lot of modern martial arts training is focused on preparing practitioners for competition - training focuses on developing muscle strength, coordination and combat.
We don't compete - our training includes all the above but the primary focus is on training for the cultivation of qi, not to excel at competition. Internal not external.
My martial arts training complements my Druid studies.