En période de forte charge de travail, il a souvent la tête dans le guidon.
During periods of heavy workload, he often has his head down and focused.

Depuis qu’il a commencé à préparer ses examens, il a la tête dans le guidon.
Since he started studying for his exams, he has been completely focused on them.

Elle est tellement absorbée par son projet qu’elle a la tête dans le guidon.
She is so absorbed in her project that she has her head down and focused.

Les jours qui précèdent une compétition, les athlètes ont souvent la tête dans le guidon.
In the days leading up to a competition, athletes often have their heads down and are focused.

Il faut qu’il termine son rapport à temps, il a la tête dans le guidon.
He needs to finish his report on time, he is completely focused on it.