I've came across this one page comic panel about an apprentice girl and her teacher, the teacher then give her a job which he said will be "handy" (手頃な) for the apprentice but the truth it is actually not.
After she done with her job, the apprentice said this:
あなたの「手頃」は本当に信用なりません。しっかりしてください。
So what does しっかりしてください mean in this? I have known that it has some meaning like "Pull yourself together/Get it together" but I do not think it will suit with the above context.