It's the prevention of migraines during daily life that's important, not dealing with migraines when they occur.

They deal in software products.

He is hard to deal with.

I made a great deal on a new car.

I deal in second-hand books.

He was accused of double-dealing in the business deal.

Plain dealing is essential in business transactions.

There's also a great deal of so called behind-the-scenes work.

Thanks to Sharon’s negotiation skills, we sealed the deal.

It's not a big deal.