St. John Neumann was a holy priest and bishop, always striving for perfection in his life.
For example, while in seminary he wasn't satisfied with the daily schedule of rising at 5:00 a.m. and made a personal resolution to always wake-up at 4:00 a.m. It was a daily sacrifice that he believed would help him on the road to holiness.
However, he wasn't always able to stick to that personal schedule and was frustrated with himself when he failed.
He wrote about it in his journal, which is quoted in the book The Life of John N. Neumann:
My soul, what a miserable day! We have displeased our God by our inconstancy in good resolutions. Although awake at four, I failed to rise promptly, owing to sloth and carelessness. The thought of my unfaithfulness haunted me even in prayer and I found no consolation. O my soul! Acknowledge thy sloth and ingratitude!
Even though what he did was not sinful, he still held himself up to a much higher standard, not being satisfied with "average" holiness.
Whenever he failed in his resolutions, he turned to God for grace and strength, recognizing God's merciful gaze:
If the Divine Master should reject so sluggish and disobedient a disciple, thou wouldst surely forfeit eternal happiness. How easily thou mightest have fallen into some great sin, if His grace had not shielded thee! What wilt thou do with this poor soul of mine O Jesus?
His example reminds us that saints weren't perfect and were often frustrated with their weaknesses.
Their weaknesses kept them humble and opened them to God's grace. We too should recognize how we fail, while at the same time relying on God's strength.