My nerves are shot!

I got a counter offer on the house this morning and for some reason I am freaking out!  I'm thinking it's because of the huge amount of money aspect of it.  I was slightly freaking yesterday while at the bank and talking numbers.  I majorly freak when I become newly responsible for very large sums of money.  I did it when I bought my first place and again when I got my car.

I think I am more so now because I need my mother as a cosigner.  I have always paid all my bills on time and have no doubt that I would in this place, but there's still that huge thought of "Oh no! What if I'm really screwing up and end up hurting my Mom's credit too??"   I hate that I even need her to cosign.   I've got great credit, but just not enough income to qualify on my own.  And with renting and paying off old debts it's so hard to save any away.  The mortgage payment will be cheaper than rent now, so I know that'll help.

It's just a little scary right now.  I keep trying to tell myself that I've done it on my own before and will be good this time too.  I know once I get in the house and everything settles I'll be fine, but until then I just need to calm my nerves.  (Did someone say cigarette?)  The realtor is currently talking to the sellers to see if they're cool with a rearrangement to their counter.  I'm thinking they'll accept it because it's just a little thing so the extra can be put in the mortgage payment instead of being paid upfront.  Gaaahh!