I'm glad you're not depressed ;)
Re: tiredness, it seems that this is the one thing all us strokees have in common. I don't know how long since your stroke but fatigue still seems to be an issue even for long termers.
I don't know if this is true or not but it is how I make sense of it all. My brain is busy forging new connections & pathways and on my bad side fewer muscles & muscle fibres are firing to move that side of the body - so of course I get tired.
My advice would be to restructure your day to build in sufficient rest. Maybe you didn't need to before but things are different, now aren't they?
Rest is a really important part of recovery. I was told a useful rule of thumb - if you can't do today what you did yesterday, you did too much yesterday.
I echo Sues comments. One of these forums asked what was the most disruptive deficit of their stroke and about 80% mentioned fatigue. It very slowly gets better.
I look at it as your affected side is only working at maybe 50% but you still are trying to push it to 100% to overcome spasticity and your good side is working at 200% to make up for your affected side. So in order to keep to what was a normal day your are expending 3 times as much energy. You mentioned tennis. I think tennis is one of the games for the Wii and that might be a good therapy for you to consider.
Hang in there, its a long road to travel but you can get there.
I definitely agree with the other two posters. People, even professionals will act like they never heard of such a thing. They also tell me the same thing about my lack of physical stamina. I know differently because on days when I overdo it, well, the next day or two I pay for it and have no energy at all so I'm learning to pace myself, even with my rehab exercises. After all, what good do the exercises do if I do everything the PT assigns one day only to end up in bed resting/sleeping for the next day or two, unable to do 'any' of the assigned exercises? I definitely agree, pace yourself, learn how much you can do each day and don't do more or you will pay. Stamina will grow but most likely very slowly.
I had a stroke back last Oct, and I was very energetic when I came back home, was ready to recover and start a new life, and suddenly Jan 2009, I began feeling really tired, and would sleep my whole day away. I thought it was the medication, I refused any pain medication, for the headaches, however they had me on antidepressants for depression. So many people suffer depression after a stroke, however blood tests just revealed that my thyroid levels was very abnormal, and now I am taking medication for that also. So I've been on this for a week now, so I wish you the best of luck. Be perisistant with your doctor, and never give up.