Slowly, slowly is the only way to go. If you use similar techniques as Pat Parelli's horse training you should see results. Things like ignoring the cat, not watching it in an obvious way will help it believe that where ever it is resting that you haven't seen it yet, I use this technique sneeking up on wild birds and it's amazing how close you can get when all your energy is not directed at them. This technique will be good for most times that the cat is loose in the house and your just going about your daily activities.
If you can get the cat contained in one room and you shut the door and sit or lay yourself down and eat a snack, have a drink and read a book the all of these activities will show the cat that your totally uninterested in it and it will usually begin to relax. A sudden move may still give it a shock but as long as your are still not making a move towards it the cat should relax again. You can even add a bowl of the cats favourite food into the mix, starting off with the bowl furtherest away from where you have stationed yourself, and then gradually over time bring the bowl closer to where you are sitting, all the while pretending to pay the cat no attention. I used this technique with a wild galah that I had rescued and its wing had been amputated (poor thing's wing was totally shattered and unrepairable), and it had to have ointment put on the stiched up stump daily. This bird was savage and scared out of its wits with the treatment but once I was able to start working with it in a confined space, ignoring it by reading a book and only occassionaly saying it's name and it began to trust me and would make its way over to me on its own accord.
When ever you are about to do any conditioning/ training with the cat be sure that you have the alloted time for that day (for example 3 minutes in and your rushing off to greet visitors that you knew where coming over), and be calm and peaceful in yourself. Watch your fish for a bit and get into a tranquil frame of mind with no distractions, if your calm the cat will pick up the vibe and help it be calmer too.
My remaining cat (her brother died of cancer and a brown snake killed her sister) from a feral litter of kittens that I found at work and handraised is the most loving friendly cat towards my husband and myself, but she has never trusted strangers and even other family members when they come to visit she runs and hides and takes hours to come back out and is jumpy until she is sure they have gone. She will approach my Dad provided everyone else is gone. Dad usually just lays down on the couch and watches the TV so his focus is not on Spook, if she does decide to check him out he usually just moves one arm towards her, rubs his fingers and makes smooching noises to coax her over. All of these limited activities shows Spook that he is wanting to be friendly to her but is not pinning all his attention and frustration of her not coming to him on her, it's more of a come on puss come over...oh well you wont I'll just watch the TV again attitude. I watched my Dad do the same thing with orphaned Joey's that I was raising (true joey's demand attention but sometimes I had to do something without them in tow and I would get Dad to entertain them while I snuck away from the joey to do what I had to do), and all he did was reach out a hand, coax them to him, give them a rub and still watch the TV.
Hope these ideas give you some insight into helping your cat calm down, it deserves the chance to know that humans can be nice.
