Idioms with ON

On the contrary- Just the Opposite

Ex- I did not reject his call; on the contrary, I spoke to him for an hour.

Many people believe that early mornings are peaceful, but on the contrary, they are often the busiest part of my day.

He thought his new diet would make him lose weight quickly; on the contrary, he's gained a few pounds.

She didn't find the criticism discouraging; on the contrary, it motivated her to work even harder.

On the horns of dilemma - caught in a dilemma

Ex- The company was on the horns of a dilemma: invest heavily in new, unproven technology, or stick with their outdated but reliable systems.

He was on the horns of a dilemma when his two best friends both asked him to be their best man for weddings on the same day.

On the wane - declining, decreasing

Ex- Due to his rough behavior, his fame is on the wane now.

The storm's intensity is on the wane, and we expect it to clear completely by morning.

The old traditions of the village are definitely on the wane as younger generations move to the city.

On the whole- overall

Ex- On the whole, he performed well in this project.

The movie received mixed reviews, but on the whole, audiences seemed to enjoy it.

On the whole, the weather during our vacation was beautiful, even with one rainy day.

On the whole, the new software update has improved system performance, despite a few minor bugs.

On the spur of the moment- Under pressure, Under the impulse of the moment.

Ex- He has to take this decision on the spur of the moment.

She bought the expensive dress on the spur of the moment, without really thinking about her budget.

Sometimes the best adventures happen when you act on the spur of the moment.