Many people have what I will call a “threshold of impossibility”. This is a limit above which something is considered as either taking too long or being too difficult to do. This could either be because they aren’t putting enough effort into it, do not realise they can put more effort into it, do not yet have enough practice at it, or are too impatient for it. An example of this is meditation. Meditation requires large amounts of focus and, discipline and training to do usually. The same goes for martial arts, difficult academic subjects, exercise, cognitive skills and mental abilities. This is especially true when one has exhausted all of their known options for trying to do something, as repeated failure is more likely to convince someone that something is not possible. This also happens when someone does not know how to do something, as often trying to think about how to do something without sufficient information or enough practice in the logic needed to figure it out can make it extremely difficult to do.
However, in all of the examples listed above it is usually harder to actually determine whether or not something is impossible. Without thorough testing and certainty, it’s hard to determine that there are no possible ways to do something as this requires you to either prove that the end result is not possible, or that every method to do it will fail. Proving the first would require that you show that no matter what the method used, the end result would be illogical, and the latter would require that you determine every method to do it, and prove that they don’t work.
People’s threshold of impossibility decreases the harder something is, the more they fail, the longer it takes, or the less confidence they have. In the opposite situation, when someone achieves something they didn’t think possible, their threshold of impossibility increases, and now they think more is possible.
Do not confuse that which is hard with that with is not possible.