Should I go on a holiday I can't afford?

I have been invited by my mum to go to QLD (I live in Victoria, Australia) in August and I really want to go as I am 23 and have never been on a plane or been anywhere out of the state for a holiday.

My little sister has her aerobics championship there so they are going up for a weekend but will also be going to the theme parks.

The only problem is the timing, I have a maxed out credit card, no savings, what money I am getting from working full time is going to my rego ($712) at the end of this month and my car service ($500) at the end of July. Plus a holiday my partner and I planned mid July to the snow. Not to mention general food and transport costs on top of this. In other words, I'm screwed for money at the moment and trying to just pay things off and save...

I really want to go and my mum is nagging the hell out of me but should I? I will have a spare $300-$400 by August but if I spend it I will be back to square one and won't be getting in the green until late August.

I hate my job and desperately need a good holiday. Would you do it for the sake of a nice holiday even though you know you could not afford it?