All the pleasureful experiences we have in our bodies are really based on yichud. Gilui yichud, the revelation of G-d's unity and presence is established through the efforts of man. Many of the things we do are a revelation of what we think of ourselves in relation to G-d, reality and truth. Fulfilling mitzvos reveals G-d's presence, whereas sinning conceals His existence. Man has a choice about which path to take, as his actions have a universal impact. From the darkness of a sin, can come suddenly the ultimate light. Which will we choose?