be only half the battle (won)

To represent the completion of only an initial portion of the process needed to achieve a certain goal or outcome. Often implies that what is left to do will be as or more difficult than what has been accomplished. We finally got the CEO to approve of our plan, but that's only half the battle won. Now we need to deliver on a project that lives up to our promises. Dredging the car up out of the lake was only half the battle. Getting the thing drained out, dried off, and back in working order again will be the real trick! Yeah, I admitted to my family that I have a problem with alcohol, but that's only half the battle won. Now, I have to go to rehab.