Assuming you will have something before you actually have it; similar to "counting your chickens before they hatch" (which is commonly attributed to Aesop).
"The Mariners could do better than expected this year."
"Let's not kid ourselves. Check your premises before you make a prediction."
"I'm assuming a number of things go right. Maybe I'm just counting my monkeys before they're out of the trees."
Nickname given to bales of marijuana thrown overboard or out of airplanes. Origin is reportedly from members of the US Coast Guard in the area of Southern Florida.
"Base we've got some square groupers floating outside of Miami harbor."