There are a few things that characterize a flow of water:
1. There is no force, it is just flowing, naturally, without trying to and without forcing the water to flow.
2. There is no pulling or pushing, just as the water comes, it also goes. It's a flow.
3. In a river or creek, there are areas where the flow is rough and chaotic, and there are areas where it is calm and gentle, and yet, it is all part of the same flow.
I think this is a good analogy for life:
We should not try to force things, we should move along with the flow rather than against it. If thoughts and distractions arise, such as anger, hatred, or other negative emotions, or even just unwanted and uncontrollable thoughts, just as in the flow of water where there is no pulling or pushing, there should be no pulling or pushing of the thoughts. Just an allowing of them to fade away just as they came. At times life will be difficult, rough, and chaotic, but there will also be times where its calm, gentle, and relaxing. All of it is part of life and we must all go through this, because it is the flow of life, and going against it will only make things worse. Trying to force things, trying to push thoughts out, and trying to skip around the rough parts will just make life more difficult than it is.
Letting go of thoughts to me has always felt like a task to do while meditating, and that is not the point of the meditation or of letting go of thoughts.
Rather than it being a task and something you are actively doing, I think of it more as allowing the thoughts to pass. To not try to force them out, but to just let them be. In my mind, and it may just be me, but thinking "letting them go" always felt like its something I need to do, and that is adding another thought to your mind, the thought of needing to let the thoughts go. So instead, I see it as allowing them to go, letting them be what they are - passing thoughts.
I like the analogy of a flow of water in a river. Nothing is pulling and nothing is pushing. There is no force applied, and yet there is flow. This is how I try to see my thoughts while meditating, and in general in life. Just as they came with nothing pulling them in, that's how I should let them go, without anything pushing them out.