But my dear this is not wonderland and you are not alice meaning

This is an expression that basically means something like: "yes, but we are in real life."

Explanation:

Often used to bring someone back from reality after an enthusiastic discourse about something that most likely will not happen, this expression basically means that, unfortunately, it going to stay an imaginary thing; reality is quite different than fantasy.

Life is not a fairy tale and this is sadly the reality we live in.