Bad Luck!!!! How about no Luck

I've come to realize I have no luck...It's just a matter of time before the best of things that I think are great, come toppling down like a house of Cards...3 years ago I Spend a week putting in Central Air to save about 2 thousand dollars. 1 Dog w/ big bladder + AC unit equals disaster, and if anyone could have told me that then you're full of shit. How does Dog piss eat a copper coil...But I digress. I get a new Unit for about 800.00 hoping to save 1200.00 that the local HVAC guy told me it would cost to replace. I proceed to put it in, should have taken 4-6 hours three days later it's in. And guess what...It doesn't work and I need to tack it back to the manufacturer. When will I wise up and pay the extra....