Everyone knows how a monkey trap works.
Stick a banana or some enticing object into a jar or bottle with a hole small enough that a monkey can fit his hand in but cannot take a clenched fist out.
The monkey reaches in for the object, and then is stuck because his attachment to the object overwhelms his ability to simply let go and regain his freedom.
This is a good metaphor for much of the suffering we experience. We are stuck in a bad mood after a long day and simply refuse to let go. A thought that we might be sick, have COVID, or cancer enters our mind and we hold onto that thought so firmly that we indeed truly start to feel every little thing that makes it true. Unable to let go of the thought or feeling, we remain stuck in negative mental states and perpetuate our suffering.
In the moment, it is never easy to let go. It is a trained ability, something we need to familiarize ourselves with. Learning to work with attachment, fixation and grasping is the main work of meditation. Gradually, we find that we can let go, that we can discover enough space to break free, that we can experience negative mental states and intense emotions and not be overwhelmed by them.
The monkey experiences suffering and bondage because he doesn't recognize that freedom is a choice: a willingness to let go.