a monkey on your back
monkey on (one's) back
1. slang A drug addiction. Did you hear? Pete checked himself into rehab to deal with the monkey on his back. I've been clean and sober for nearly five years, but I can still feel the monkey on my back breathing down my neck.
2. A persistent burden or problem. This project is such a monkey on my back right now—I can't wait for it to be over. Trust me, don't get in debt. You don't want that monkey on your back.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
a monkey on your backJOURNALISM
If you have a monkey on your back, you have a problem, often an emotional problem, that makes your life difficult for a long period. They haven't beaten United in three years and it's a monkey on their backs that they are desperate to shake off. Note: You can also say that you get the monkey off your back, meaning that you manage to end the problem. I'm just delighted to win and get the monkey off our back with a home victory at last. Note: `To have a monkey on your back' originally meant to be angry. Later it came to be used to say that someone was addicted to drugs; it is still used in this way today.
Collins COBUILD Idioms Dictionary, 3rd ed. © HarperCollins Publishers 2012