get it over with

Banana Yoshimotoの "Kitchen" を読んでいます。
Everyone out on the streets was coming and going, looking happy, the light shining through their hair. Everything was breathing, increasingly sparkling, swathed in the gentle sunlight. The pretty scene was brimming with life, but my soul was pining for the desolate streets of winter and for that river at dawn. I wished my heart would break and get it over with.
"get over" で打ち勝つとか克服する意味がありますが、"get it over with" はこれで慣用句として覚えた方が良さそうです。辞書に説明があるか見ます。
・Wiktionary: An exhortation to do something quickly (typically because it is unpleasant).: I know you have to draw blood, so go ahead, get it over with!

・Farlex Dictionary of Idioms: (idiomatic) To do or finish, especially said of something unpleasant.: He didn’t want to go to the doctor for his shots, but he decided it would be better just to get it over with.
"get over" は困難に対峙していますが、"get it over with" は 'typically because it is unpleasant' な事に対して使われることが多いのですね。