If you’re not able to pay the full extra payment right from the start, there are ways to get there and still accomplish the early payoff.
Any time you get a raise, rather than incorporate it into your budget, use it to make an extra payment on principle.
Make this a habit every time you get a raise, and you’ll gradually hit your number.
Use your tax refunds to make extra payments on your mortgage each year as well.
Side income and any bonuses should get funneled into extra payments at every opportunity.