You may not know how you could possibly complete a task until you begin it.
God does not often give us the strength to complete our work before we begin working.
I have pain that reduces my energy and health problems that reduce my strength. It is not uncommon for me to begin work feeling as if I did not have the strength to complete it.
He supplies strength to work as we begin working, as we continue working, and as we finish working. Moment by moment, hour by hour.
Plead with God for strength to begin, then do so.