Thanks for answers, guys!
For discipline, I actually invoking earth element for a really long time, little by little it strengthens my discipline but for now, not at the sufficient level. It still needs time. But I will try daily walking, if you say so.
And I searched but I'm not sure about I understood it properly. Yang foods are making your body hot, right? Like hot coffee, black tea etc.
And if I have so much yin energy, should I cut out doing hatha yoga and go only with kundalini yoga to balance? Or yang will increase anyway even if I don't cut out hatha?
Look at a kapha-diet guide and it will show you foods that are light and promote yang energy or removal of dampness. Yang includes hot, but not always. An example of what I mean is like substituting salmon for red meat, as the salmon is less dense. Another example includes brown rice or carrots over potatoes.
Don't beat yourself up over your diet and feel bad about eating. It is just a matter of eating the right foods in each group that promotes for the body to have more yang energy overall. Denser or colder foods, such as milk, bananas, and butter, will stagnate a body that is already dealing with yin-excess.
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Fat is a yin PATHOGEN, meaning it is not supposed to be there. That is different from something like blood or bone marrow, which is healthy yin. You cannot really have an overabundance of healthy yin or yang.
Hatha yoga promotes mainly healthy yin and balance, but in this way, it eventually leads to more yang as well. Yin and yang complement each other. Of course, there are spiritual benefits as well. All yoga is good for every body type, although some may be better than others. So keep doing the hatha yoga; it will help, not hurt you.
In comparison to kundalini yoga and hatha yoga, cardio exercise is very yang. If you can, steadily increase from walking to fast walking, and then light jogging, and so on. If you have knee pain, then perhaps switch to an elliptical instead. Aim for being in a mild sweat, with moderate exertion.