Some years back my live-in girlfriend (and now wife) came 
home while I was napping on the living room couch.  I was still 
half asleep when she leaned over me to try and get a kiss.  I 
wanted to say "don't get your hopes up" but then thought 
maybe "don't jump the gun" would be better.  In my half-awake 
state it came out "Don't get your guns up."