Gains goblins. Those things in your life that rob you of what otherwise would be your hard-earned gains on strength, muscle size, endurance or whatever other thing you want to develop by training.
It can be anything: a person (like that gym bro that maybe distracts you more than it's good for you), a medical condition, a commitment, or what is usually most common (and be honest here, because for most people it is one in this category), a bad habit of yours, amongst others.
Feel free to share.
Periodically I get depressed (more than usual), stop exercising and my muscles waste away
Same here
Also I live in a country in the southern hemisphere where the heat takes away my desire to do anything, let alone exert myself and raise my body temperature