The budget will be balanced in 10 years. Why 10 years? Trump expects he would survive in 2 elections (8 years). Wishful thinking!
In 10 years, no one will remember the promise and Trump could be dead by then (due to old age, too much Volka, or...). You can cheat all folks all the time as long as long as you extend your promise to the time you could be dead. Smart business decision!