It is an old Catholic custom to offer to God as a sacrifice the annoyances and crosses of each day. These short prayers are usually expressed along these lines:
Short prayers of this kind, also called aspirations, help us to avoid giving in to irritations, discouragements, and despair. They also remind us that Jesus can unite our sufferings to his merits to use for the salvation of souls.
These prayers punctuate the day with a remembrance of God. - Using these short prayers can lead to a practice much loved in the Orthodox Church and adopted by the Western Church. This is the Jesus prayer, which consists in constantly praying the name of Jesus or the words, "Lord, Jesus Christ, have mercy on me, a poor sinner." Eventually the Jesus prayer can settle into the rhythm of one's breathing and enter into the heart in a way that is truly sanctifying.
Our Lady of Fatima suggests not only offering sufferings that come to us unbidden but also offering sacrifices, especially for the salvation of sinners (including oneself, of course!). Such sacrifices could consist in fasting, saying prayers, or undertaking unpleasant tasks that could have been avoided.