Y.C.
I have a 2.5 year old too, and some mornings we've been dealing with the same thing. We have found that if she is really unreasonable, and there's nothing wrong (not sick, not needing to potty, not hungry, etc) it works to tell her that she needs to go back to bed until she can stop being so mad and sad. We put her back in bed, give her a kiss, and tell her that she can get up when she is ready to, but that she needs to rest some more, so that she's not so crabby. She doesn't like this, and typically screams and cries for a few minutes with the door shut, but then she gets quiet, and a few minutes later she is usually saying she's ready to get up, and is much cheerier. For this she gets a big hug, and the day goes on.