When you go to someone's home that you know and knock on their door, what do you do next? You know they're home, so you wait patiently for them to come open the door. Perhaps they don't answer, so you knock again. Still no answer. You call out their name and when they hear your voice they open the door for you and invite you in to share a meal.
You could kick the door in and make a dynamic entry into your friend's home, force them to let you in and fellowship with you, completely taking away their choice in the matter. That wouldn't make for a good or proper relationship.
This is a beautiful picture of salvation. Jesus stands at the door of your heart and calls your name. He wants you to invite him in and have a relationship with him. He won't force himself upon you or make you receive him. That choice is yours alone. If you haven't already let him into your heart and received him, listen! He's knocking and he's calling your name.
Revelation 3:20 (NLT) - "Look! I stand at the door and knock. If you hear my voice and open the door, I will come in, and we will share a meal together as friends."