很简单
as又可以被换成the way 两者意思相同 表示比较
例:I feel as if/as though there is never enough time in the day.
as if又可以被换成as though 两者意思相同 表示像 用来形容行为或感受
例:Spending time alone doesn't bother me as/the way it did when i was younger.
like可以代替as as though the way as if 表像或比较
例:I feel like there is never enough time in the day.
Spending time alone doesn't bother me like it did when i was younger.