Step 1: Panic Sell: Quickly go to your exchange of choice (preferably one located in a country other than your own) and sell all your bitcoin. Don't even risk owning the smallest fraction of a coin. If you really want to commit to quitting, do it right and sell everything.
Step 2: Seek Validation on Your Favorite Bitcoin Forum: It is simply not enough to sell all your bitcoin. To ensure that you later don't have a "change of heart," it is required that you announce your departure. Regular bitcoin users also like to see who is leaving, so it is important for you to tell them. You won't believe how much strangers on the Internet care!
Step 3: Make Sure You Know Your Talking Points: People leaving bitcoin need to have a reason why. Make sure you have one in your pocket especially during step 2. Please choose one of these: "Price Volatility", "Centralized Mining", "Fixed Supply".
Step 4: Enjoy the Freedom from Bitcoin Shackles