Pain

no pain, no gain

Meaning: it is necessary to work hard or strive to reap rewards

Example: If you want to win the title next month, you have to train for an extra hour every day next week. No pain, no gain. Read on

pain in the neck

Meaning: Mathematics is generally a real pain in the neck for most of the school and college students.

Example: Mathematics is generally a real pain in the neck for most of the school and college students. Read on

bite the bullet

Meaning: to endure a painful experience that you cannot avoid

Example: When the time comes, I'll bite the bullet and take my punishment without a fuss. Read on