'gather courage' is correct and usable in written English.
You can use it when you want to encourage someone to face a difficult situation with courage and strength. For example: "No matter how hard things get, always gather courage and keep going."
"It's important to gather courage, fight laziness, and work".
As Mr. Hughes spoke, he seemed to gather courage, and he soon let on that he had chosen a candidate and that this person had a doctorate.
As you pass the person of interest, you gather courage and lift your face, despite everything, but the person of interest is talking to somebody else, and so you keep on going, all the way out of the party and the dorm.
I did not know yet that there would be days of surprising grace, nor that one of those days would come in Kuwait when, my resolve sapped by exhaustion, heat, and anxiety for the war I was headed toward, I would gather courage from following my brother-in-law, a fellow officer in my unit, onto the plane to Kandahar.
As the traffic races round the Piazza Venezia, and brave pedestrians gather courage to cross it, it is perhaps hard to imagine that this was the most sacred of all the places that fascism sought to turn into symbols of its power.
In more than gentle words, avoiding hurting the sensitivities of the numerous deniers who populate the Congress, Francisco urged the audience to gather courage to "redirect our steps" and avoid the catastrophic effects of climate change caused by human activity.
She started to scuttle away, then gathered courage and addressed him".
The election is Sunday, and the campaign has suddenly seemed to take on weight and moment, with Mr. Milosevic trying to beat back the challenge of those he considers traitors, while the opposition gathered courage from numbers and from the obvious nervousness of the regime.
Although the attack took place on Monday night, the family of the woman gathered courage to go to the police on Wednesday afternoon.
