While installing a fan in my bedroom, I slipped off the joice because of bad knees, causing a( t ) type of crack extending to about a foot which looks like a stress crack in my bed room. The crack is no where around the fan. I have spread a powered mix with water serveral times and let dry only to look like a bad job. Is there a way of doing a better job. Thank you

If it's not too deep, caulk, believe it or not, works great. It seals, but also endures expansion. It's great for spots where walls meet, or where walls meet ceilings.

XenoSapien

You should mud and tape the crack. If it's along the drywall joints you should put in some new screws as well since you may have "popped" the drywall loose.