Let's let Rabbi Akiva answer your question. Yes, it's the old "drip on the rock" theory. Rabbi Akiva realized at age forty that just as a sustained trickle of water can carve rock, so too sustained Torah study can change our heart. Solid change can be achieved with constant, daily, study. So, study works about negative speech and judging favorably every day (Examples: books such as "The Other Side of the Story," "Courtrooms of the Mind" and "A Lesson a Day"). Even a few minutes a day will, over the course of time, create a change in you.
And don't forget to judge yourself favorably too. Be happy with any change, no matter how incremental.
If you find yourself speaking negatively with certain friends, you may need to get different friends. Avoiding people, places and situations that trigger forbidden activity is great way to change one's behavior.
Here's a stratagem to help you feel positive even towards people who annoy you: When you see someone doing something that bothers you, and you think to yourself "What an obnoxious boor," imagine the person as a little baby. Picture his mother's unqualified love for him and her joy as she holds him in her arms. Now try to feel a little bit of that love.
