It is a critical mistake we've done easily that we assume that we already know what people think.
-> It is a critical mistake (we can easily make/we tend to make/we are prone to make) to assume that we already know what people think.
-> To assume that we already know what people think is a critical mistake we are prone to make.
Making brief time to write sincere words once a week will bring you something meaningful.
->
Most people do not appreciate/acknowledge that Washington was a wise military leader.
-> Washington is usually not acknowledged as a wise military leader.
Losing moisture from excretion and evaporation must be continuously replaced.
-> Moisture organisms lose through excretion and evaporation must be continuously replaced.
What makes us real human?
-> What makes us really/truly human?
More similar point is that two subway systems cover the wide area with cheap fee for commuters.
-> More similar point is that two subway systems cover wide area at a cheap fee for commuters.
-> A further similarity is that two subway systems cover wide area at a low cost for commuters.