half the battle
A large part of what it takes to accomplish something.
Knowing is half the battle. ― It is necessary to be informed in order to do the right thing in a given situation.
Courage in danger is half the battle. Plautus
The first blow is half the battle. Oliver Goldsmith
Knowing that you possess a talent is half the battle in mastering it. Lin Carter
A good beginning is half the battle. Vietnamese Proverb
A strong attack is half the battle won. Spanish Proverb
A bold onset is half the battle. German Proverb