(placed in quote box for ease of use)
If you believe that the outside world exists, then play along with me.
So lets say that you are the mind. You only exist in your internal reality. Let's say those "other people" out there either also exist in their minds, or are just part of your mind, play along if you don't think that's true. They exist in your internal reality, and you prefer to work with them in that sphere.
Ok. Now lets say you experience things in your mind. Well you can't just experience whatever you want, you have to navigate certain mental limitations and barriers. If you can't effectively change the way you see things, then you'll frequently be experiencing discomfort.
Let's get a little more involved in this imagination game.
Some people approach you and they want to navigate limitations. You tell them whatever is convenient to tell them at the moment - let's say it's something that you know isn't true but you doublethink into believing it is true. Does this ultimately help YOU (they are just in your head, hence you)?
Let's say you do the same thing for yourself (redundant, in this case): you tell yourself what most is convenient with doublethink. Does this ultimately help you?