The phrase "keeps one's shoulder to the wheel" means to persevere in a difficult task without giving up or becoming discouraged. Some synonyms for this phrase include "puts one's nose to the grindstone," "sticks to it," "perseveres," "maintains focus," and "grinds away." These phrases all suggest the idea of working hard and not letting distractions or obstacles get in the way of achieving a goal. By keeping one's shoulder to the wheel or using one of these other phrases, it is possible to stay motivated and work towards success even when faced with challenges.