Is it haram to lie to yourself in Islam? Are Muslims allowed to self-deceive for Islamically good purposes?

A lie is a figment of your own mind and therefore you are always and yet never lying to yourself. There are different types of lies and some are considered acceptable by society although lying in general is a disapproved- but still very common- form of art. It's okay to lie if you have the right reasons I think; nothing is really ever in black or white. If your lying to make someone feel better than it could be defined as optimistic encouragement instead of a lie. Such things are basically lies in pretty packaging.