A technique that has helped me overcome many negative habits is to focus on a particular word (or phrase if you find one word too limiting).
Not to the point of obsessing over the word – simply to channel your attention towards your intended goal. For example, if you feel you wish to develop more patience, you can gently remind yourself using a single word – patience.
As with affirmations eventually the word can be dropped once it has done its job.
See also: One Word Meditation Mind Map