I find the same thing happening for me too. I have been doing this (on and off) for just over a year now. For me, it is not just funny things, but all pleasant sense-experiences, such as food, sights ect. seem to lose some of their "magic" when I try to be mindful of them. They suddenly don't seem that great any more. I do also sometimes miss being immersed in them, especially as I am currently trying to remain heedful and aware throughout the whole day.
I think in the long run, this is a good thing, as it is the beginning of seeing the Dukka inherent in conditioned things, and the drawbacks of sensual pleasure. Not necessarily a good thing if one wants to remain a housholder
. Perhaps the best advice, though I am not experienced enough to be sure myself, is to just carry on and push through it, and immerse yourself in the joy that the path gives.
If I misrepresent the Dhamma, please point it out. I am here to learn