Sabr is patience: patience with hardship, with people, with the slowness of progress. The Quran preserves the supplication of Talut's small band before they faced an army that vastly outnumbered them.
Rabbana afrigh 'alayna sabran, wa thabbit aqdamana, wa-nsurna 'ala-l-qawmi-l-kafirin.
“Our Lord, pour upon us patience, steady our steps, and help us against the disbelieving people.”
The du'a of Talut's small band before facing Jalut's army. For when the odds are stacked against you.
Rabbi la tadharni fardan, wa anta khayru-l-warithin.
“My Lord, do not leave me alone, and You are the best of inheritors.”
Zakariya's du'a for a child, after years of waiting. A du'a for anything you've been hoping for too long.
Inna lillahi wa inna ilayhi raji'un. Allahumma'jurni fi musibati wa akhlif li khayran minha.
“Indeed we belong to Allah, and to Him we return. O Allah, reward me for my affliction and replace it for me with something better than it.”
The complete supplication taught for the first shock of loss: affirming that we belong to Allah (SWT), asking for reward through the pain, and trusting Him for a better replacement in the way He knows best.