I've always seen it as accepting Christ's grace and His lordship in your life.
Belief merely indicates that He exists. Even Satan believes in Christ. Satan knows all about Christ, yet is eternally damned.
"Accepting Christ" does not imply passing judgement on God. It's more like accepting a gift from someone--you're not passing judgement on them.
In this,Jesus is saying that you must accept him,not just believe in him.You can't "believe" someone to enter your home,but you can "accept" them into your home.By accepting him,you also accept his teachings and convictions.