I meditate since a short time, but I experienced a joyfull feeling once recently. It happened when I was able to kept completely concentrated on my breathing for a longer time than usual. For me, it was not the heart, but there was a kind of light and warm feeling in the front of my head - like if it was in my brain. It was a very nice sensation and it came with a feeling of joy.
I think I read somewhere that it is better not to cling to this feeling and that we will get used to it, then we will reach an other state. Can anyone confirm that?