It may help to read the lives of the saints, both a version of "The Lives of the Saints", but more especially individual stories of saint's lives. Sometimes we find something meaningful and motivating in them. I just read St. Germaine, a poor, neglected, sickly, disabled, maltreated girl, who grew in the love of God, treated all with heroic charity, and faithfully did her duties. She died at 22, living on bread crusts. The length of life isn't important, but she definitely earned an early heaven through her suffering and early mastery of virtues. I think it was miraculous she lived so long.
Also, whatever part of your (his) duty of state he dislikes the most, finds most bitter, that is his cross. Consider how much Jesus loves us, try to put yourself in His shoes and consider that love he has for us that motivates Him to eagerly and zealously carry His most bitter cross to His most agonizing and shameful execution, so that we might be saved. We should do our part to return the favor, and for those who don't carry their cross well.
Maybe make it a part of morning & night prayer & meditation to reapply one's self to the resigned, patient, and joyful carrying of one's cross.
Reading the works of St. Alphonsus de Liguori will keep these thoughts in mind, as he often just quotes important things many other saints said. I just remembered a habit I need to pick back up; writing down the most important lines of each page of St. Alphonsus' books each day. It takes just a few minutes, and this way I will eventually condense these books to a tenth of their size.
On that thought, there already exists condensed books like: My Imitation of Christ.