Let's go rafting
There are two people who get into a raft for an hour of going down river. They don't know each other outside of rafting. This is how they met and the only way they've ever interacted. When they first started rafting together, one of the two had boated quite a bit and knew the river. They knew how the water was constantly changing, how it flowed around obstacles, and how to read things with more experience than the other. Nevertheless, if you've ever rafted, you know that just because one person has more experience than the other, neither is in charge of the raft--the river is. While one person might be able to "see" more of how the water is running that day and keep the boat safe, both are witness to the experience of the river while each is paddling (or not) in an attempt to have a meaningful experience.
This is the therapy hour
The two people in the raft are the therapist and the client. They only know each other through the experience of therapy. The river is the therapy hour. The raft then is the therapeutic relationship. Without it, there's no ride down the river. If the two people don't have a mutually agreed purpose of what they are doing in the raft and why, then the meaningful experience likely won't happen.
The rapids in the water are the emotions that arise and fill the room. Some rapids are seen but missed because the raft isn't positioned well. But other rapids lie ahead. If both people are moving toward the same emotional content, the raft can get there. Sometimes the rapids are too scary though and so one person is paddling away from the emotional content harder than the other person who is paddling toward those turbulent places.
Some rides, the two navigate a lot of big waves--other times none. Some rides there's unusual things discovered, like a new species of fish. But some rides feel the same--maybe even boring. The river can be like that sometimes.
But why are the rapids there and why is it so important to go through them? The rocks that cause the rapids are memories, trauma, experiences that have created emotional difficulties. We go through them to understand them and we understand them by experiencing them in a safe place with a compassionate, interested person. When all is said and done, the ride becomes meaningful when we let ourselves feel those difficult emotions rather than paddling so hard to avoid them.
After about an hour, the raft lands on the shore and both people get out until meeting again the following week to go down the river again. But it is always a different river. Even if some rapids form in now familiar places, how they emerge, their shape, and velocity is ever-changing. Neither person really knows what the ride is going to be like, and over time, both people end up knowing how to navigate the river very well in many conditions.