All your problems, everything that you think is really a problem. Whether there is in external space or not, what we are experiencing is in the mind. It's a great thing to understand the people you like, people you dislike a lot. Without coming to the mind, you can't experience anything else.
Inspired by the 15th chapter of the Ashtavakra Gita, Swami Sarvapriyananda gives a discourse on the nature of the Self.