make a difference

make a difference (to sb /sth) (to have an important effect on something, especially a good effect; to do good deeds; create positive change) — (существенно) изменить что-л. (в лучшую сторону); оказать положительное воздействие; ~ приносить пользу, делать добро; сделать доброе дело; оставить след; внести свой вклад

It is during adversity when one can really make a big difference. But making a difference is not about being a big hero. It is simply about leaving the bathroom a little cleaner going out, than when you came in. (Quotes on Making a Difference)

Example 1: Exercise has made a difference in her health. ( CDAmE) — Упражнения значительно укрепили ее здоровье, принесли пользу, оказали хорошее воздействие на ее здоровье.

Example 2: He wants to make a difference. — Он хочет приносить пользу (быть полезным, делать добро, изменять мир к лучшему). {Выбор русского эквивалента, как обычно, определяется контекстом}

Example 3: Painting the kitchen really made a difference. It’s much brighter in there now. (ebaby)

Example 4: This scheme will certainly make a difference to the way I do my job. (MM)

Example 5: People in Cornwall are being encouraged to come forward to make a difference to the life of a disabled child. (cornwall.gov.uk)

make a big /a great deal of / a lot of difference (to have a good effect on a person or situation)

Example: The fact that I can now organize my own time makes a big difference. (MM)

Example 2: My daughter found the site very useful ... and it made a significant difference to her final exam results.

make all the difference (to sb)

Example: Having someone to talk to made all the difference to my mother. (MM)