Thank you for giving the game a try!
The "stick" mechanic was born out of a bug, actually. At first I had a completely different game-play loop in mind, but when I added the normal jumping mechanics and the jump sound, I noticed that it played multiple times if you held down the space key.
I made the jump work by having the player object check the collision with objects with the tag "Ground", then reset the jump.
Problem is, the player object couldn't exactly differentiate between objects that are touching from the top, bottom or the sides, so it would reset the jump just by touching an object with the "Ground" tag, allowing the player to jump multiple times, creating the feeling of "sticking" if the player keeps jumping while touching an object. (So, technically, the player is jumping multiple times in the air, bumping his head against a wall, so no changes on the Y-axis, so giving the feeling that he is "sticking".)
Because I had made very little progress in the previous days, I decided to use this bug for my advantage. I made the jump button play only once if the space bar is held down, and designed my levels around it.