It means: If we don't cherish time, it will easily flow away from us, which means that time will abandon people. Because the function of these two sentences is mutual.

This sentence also warns people that the coldness of time lies in that it will not stop or restart for any reason. The only thing we can do is to seize the present time. Your choice is to do or not to do. Doing may not be successful, but if you don't do it, you will never have a chance.