Jake Burhans says forgetfulness happens when your mind checks out from what's actually in front of you. The fix: stay aware of your body and where you are. Notice your feet, your surroundings, the moment you're in, and you'll remember what you came to do.
You know why you always forget things? Because your mind is not where your feet are. You're up in your head thinking about this, thinking about that, your thoughts. You're not in the room asking yourself, hey, what do I need to remember before I leave? So if you're constantly forgetting things, it's because you are constantly in your head. You're not living in the present moment. So remember that. When you're in the present moment, you're at the gym, you're in a room, you're leaving the car, be where your body is, be where you're sitting, be where your feet are standing, and you will forget less things.