lose sight of

US /luːz saɪt əv/
UK /luːz saɪt əv/
"lose sight of" picture
1.

見失う, 見えなくなる

to forget a distant object or person, or to no longer be able to see it

:
The ship sailed away until we lost sight of it.
船は私たちが見えなくなるまで遠ざかっていった。
As the plane ascended, the city lights began to fade, and soon we lost sight of the ground.
飛行機が上昇するにつれて、街の明かりは薄れ始め、すぐに私たちは地面を見失った
2.

見失う, 忘れる

to forget about an important idea or fact because you are too involved in other things

:
In all the excitement, we must not lose sight of our main objective.
興奮のあまり、私たちは主要な目標を見失ってはならない
It's easy to lose sight of the big picture when you're focused on small details.
小さな細部に集中していると、全体像を見失いがちだ