When people say "yoga" they are most commonly referring to Hatha Yoga which is a series of physical exercises, mostly what you would call stretching exercises. It's one small part of yoga, as I'm sure you know, Daylia. It sounds like you were either doing the sun salutation a little wrong somehow or maybe you just had a structural weakness there or maybe you were overdoing it. At any rate, one can run into such problems using any physical exercise program, whether it be weightlifting, running, or Hatha Yoga.

The word "yoga" means "union"(with the divine), and it includes a number of different disciplines including physical yoga (Hatha), breathing techniques (which are great!), meditation, study of sacred scriptures, diet, and so on. A Yogi is someone who has mastered all of those disciplines. In the West people usually associate it mainly with the physical exercises, however. There is yoga for the body, yoga for the mind, and yoga for the spirit.

I'm cautious with the sun salutation and some other yoga postures, cos my back is not so strong.

I've been very well impressed by Two Bears' brand of HUNA. It works extremely well, by using what I would call a directed flow of "Chi" (life force). The Japanese call it Ki. The East Indians call it Prana. A healthy person is strong in Chi, a sick person is depleted of it. Same goes for a healthy plant or any other living thing. A lot of Chi can be gathered through improving breathing technique, as is done in HUNA and in Yoga and Qi Gong. These things are pretty universal, I find, and you come across them in most spiritual traditions...but that doesn't mean you'll hear about them in an organized religion. Not by any means.

Religion, I think, is generally a set of beliefs and rules, combined with an authority structure to largely control the outer person. Spirituality is a set of practical methods practiced by oneself to improve the inner person, and it requires no outer authority structure, though it certainly requires experienced instructors to guide novices in mastering various techniques.

Kind of like guitar or banjo playing that way... :-)

Religion purports to be a path toward knowing God. And for some it is. Spirituality is definitely a path toward knowing God, since God exists quietly inside the individual. As the individual comes to know his or her true Self better, the knowing of God occurs as a natural consequence, because they are one and the same. That's Self-Realization.

A Self-realized person tends to act in ways that are most beneficial to all concerned, and tends to genuinely care for both self and others, and does not tend to fall prey anymore to toxic emotions (such as hatred, envy, greed, etc). A Self-realized person is not weak, but readily able to stand up for himself and on behalf of others who are in need.

So, well, most of us are part way there...and with time we will continue to improve ourselves.

I like the HUNA motto: "Harm nothing with hatred." Very wise. Sometimes this is hard to remember when dealing with mosquitoes...but I'm sure it can be done. You see, the problem doesn't like in killing the mosquito, the problem lies in carrying the emotion of hatred while you do it. :-) It's bad for the nervous system on a subtle level.