I spent some time living at a western meditation centre (Goenka) and that is where I learned of the three marks of existence. Annica, Anatta, Dukha. To paraphrase his english words, things are always changing, and when the ego creates desire for what is to be different then you suffer.
I already knew this wisdom prior to the centre, but I applied it differently. I was able to see the wisdom and truth of the moment, what my mind was creating, and still experience joy in my life. During and after my stint at the centre, this had changed for a while, and I am still trying to shake off some baggage.
The feeling and unspoken rule was that anytime you want something you are creating desire, and you should immediately focus on body sensations and the wisdom of impermanence-- things are in a constant state of flux. You cannot have desire because you are creating ego and craving and causing suffering for yourself, and therefore you will never reach enlightenment. One should accept what is and not what they would like it to be.
At first, I was just going to give their way of thinking a whirl, but I was in a situation that had me completely brainwashed and the negative aspects of the centre eventually weighted on my psyche. Goenka was allowed to chant, but everyone was not (of course I chanted anyway, much to the chagrin of some people there) Goenka outlined his entire theory of the practice, before and after every sit. Guess what is was? Annica, anatta, dukha. He said annica three times a minute! You are made to feel that to want something is to create craving and then you are not enlightened. The end result was I became very unhappy, but I just focused on bodily sensations and impermanence.
You will find real peace and harmony he would say, but I never was while doing his version of meditation, focusing on bodily sensations only and the wisdom of impermanence. This creates a mind that is passive, and this can easily be abused by authority. Someone else will make your decisions for you if you do not have the strength to do so. This is what my experience taught me, and I am grateful to have gone through it.
I see nothing wrong with having joy part of your life. Yes, I can be aware of impermanence, but I am the one living my life. I am the one making my choices, not anyone else. To want is not evil. To desire does not mean you are not enlightened. The key is a deep awareness of the self, which includes the wisdom of impermanence and your desires. I know it is not my desires that are real, it is the idea of my desires. I do not really know. Yes, it is an illusion. Yes, I will stay aware of the illusion. But, I choose to keep joy in my life, and part of that involves my own desires, hopes, and dreams. I choose to have ambition. I choose to try and to go beyond myself. This isn't accepting what is, but it is propelling youself forward.