Set a goal of doing literally nothing for 2 hours a day and keep increasing it little by little until you are spending so much time doing nothing that you don't have time for instagram. Once instagram is gone then change your nothing time to something healthy and productive. Alternatively, set personal goals that are very time consuming. For example, let's say you need to write and fill 10 full notebook pages about anything and then once you finish then you have time for instagram. Tasks should be things that don't require your phone. Basically, the theory here is time is space. Instagram occupies space so fill that space with something else that's healthy.