Does this make me a grown up?

I'm very well known for being childish. Not in a refusing to grow up sense, I am just very childlike when it comes to having fun and my life perspective. Some people say "You shouldn't do that because *enter sensible reason here*..." whereas I think "Why the hell not?" and go out in the rain at 3am, or take a trip to the park just to feed the ducks in the middle of winter. It doesn't make sense, but it makes me happy and I think that's the point of life.

But lately I've started coming up with the sensible reasons and I'm starting to feel a little old. When I get invited out on an evening I have to work out what time I'll get home to make sure I get enough sleep. And the more I go furniture shopping, or spend time online looking into the cheapest phone/broadband combo (it's Sky right now by the way) the older I feel. I've even signed up to Ikea Family today to get discount on the bedroom furniture I'm buying tomorrow.

So my question is this: Does it make me a grown up?

Am I finally succumbing to age and all things 'adult'? Do we all reach a point where fun things become childish and silly? Or is it a state of mind that you sometimes forget but never lose? Have I just forgotten my inner child temporarily?

I like to think it's the latter and that I'm just a little worn out from working and trying to organise moving at the same time. I want to believe that once we're in the new flat it'll be back to fun and games, late nights for no reason and general silliness. I'm hoping to keep all the boxes from moving and turn the spare bedroom into a fort for a while, but I think my plans will be scuppered by the need of storage space in the spare room.. I may convert a corner of our room into one for funsies though..
I can feel the child in me screaming for attention and to be let out to play, so honestly I do think it's just a state of mind. I'm being old because that's what my life needs right now, but when all the sensible things are finished I'll be right back to being ridiculous and outrageous for no reason other than "Because I Can."

Anyone else feeling this way at the moment? Or at least know what I mean? Please tell me I'm not going crazy. :p