"But what if I fail at stroke rehab?"

Blatently reused from Seth Godin;

"But what if I fail?" 

So what?, your doctor should have told you that failure will be part and parcel of your recovery. 

There are these 8 Japanese Proverbs about Success and Failure
Failure is the basis of success. (Meaning: Failure teaches us what actions should we change in order to achieve success.)
☯ A three days monk. (Meaning: A quitter. One who cannot stick at nothing. One who gives up as soon as difficulty arises.)
☯ The rain comes and it hardens the earth. (Meaning: After the adversity, we become stronger.)
Read Peter Levines' book - Stronger After Stroke
☯ A thorough examination of the “bad tools”. (Meaning: A bad workman quarrels with his tools (blames his tools). A loser always makes some silly excuse.) 
My therapist isn't giving me the proper exercises, my clinic doesn't have this technology. Nobody is telling me the way to recover. Whine, whine, whine.
☯ Practice rather than theory.
In our case we don't have a theory so the only thing we can do is practice.
☯ Loser is winner. (Avoiding damaging battles. I’d rather be happy than “right”.)
☯ Necessity is the mother of invention.
☯ Even Buddhist teachings scripts have some calligraphy brush slips. (Meaning: Even the greatest expert or master sometimes fails. Even Homer sometimes nods. Anyone can make a mistake. Nobody’s perfect. Everyone makes mistakes.) 
☯ Black paper is small but spicy. Small actions may matter. (Meaning: One can make a strong impact in spite of his/her particular difficulties, like small body etc. A little body often harbors a great soul/mind. Small head but great wit. Sometimes a little action can change things a lot.)

And a couple Chinese ones 
http://thinkexist.com/quotation/failure_is_not_falling_down_but_refusing_to_get/152465.html 

“Failure is not falling down but refusing to get up.”

“To talk much and arrive nowhere is the same as climbing a tree to catch a fish”

“If you get up one more time than you fall you will make it through.”

“People who say it cannot be done should not interrupt those who are doing it.”

“Teachers open the door, but you must enter by yourself”