The reason why Li Bai wanted to escape the troubles of the outside world and slip into quietness/calmness is that it seemed like he wanted to have some alone time to relax and think to himself while having his enjoyment in his life. In general, we all can be respectable beings based on our actions and we can have a respectable/enjoyable life from the people around us along with our responsibilities. But we all need a break or some space away to think and know what we are going to plan to do next for the future. This tells me that the human nature slipping away from times of trouble is a type of relief because people normally do not want to live under troubles, worries, or fears since those things can make a person's life uneasy and so getting relaxation by slipping away can help make a person's life easier along with the mood being more easygoing and calm. Responsibility is important which is why it is always best to finish our duties and get them done, but most importantly is to not worry yourself with those responsibilities by taking some time to relax and having a break especially if it means escaping for some time alone.
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Today there is really not much peace in the world and even back then when Li Bai lived. So i think Li Bai just wanted to go somewhere he left accepted and had peace with everything and everyone. Basically just wanting to slip away during bad times.
