When I had my 1:1 with my boss today, I told him at the end of the meeting that I would start my vacation after today. He said "Try to be relax and enjoy your vacation". I replied "Sure I will". Then he said "No. You won't. Nice try though". What did he mean by "No. You won't. Nice try though"? Was he just joking?
nice try M. Webster Dictionary
—usually used in an ironic way to say that an attempt at something was not very good or was not a nice thing to do
Meaning, in the limited context given in this question: Nice try though. You will not enjoy your vacation because of x!