It is definitely one of the hardest parts of sharing life with a pet, dog or cat. He will always be a part of you, and even though it is hard to do, you have to think about all the good times, the fun things you did together, and move on knowing you gave him a wonderful life, the best he could have had. It will be tough for a while, but the time will come when you find another, and even though he will never take Merlins place, you will love him just as much, and Merlin will be proud of you for doing so.
We lost this little guy in Feb of 2010, one of the hardest days we ever had. WE still had his grandson and within 2 months we found our other little guy. You know what is really neat about it, Zeke had his own personality, Pepper has his and little Leo, the new kid in the house has his, and that is what we will always remember.
Out thoughts are with you Luckysump