It seem I don't have time to do both things at once. The more your into one thing. I get to lose track of time and trying things together. The thing is one is coding and the other thing art and 3D modeling. For beginner it would the hardest part to get it working. There tons of different ways to code to make a game. But it is nothing is impossible to code if you put your mind to it. Being creative to make something that is an idea or better but the ideas are never bad. Bad ideas can make something out of it if left in the pile.
If thing goes in the wrong direction when your start out the project. There are many road blocks. Start on a goal and take notes. Cross off which doesn't work and leave as other time. If there many thing to build from the ground up or to mod off. Rethink and might get some thing new from new or old ideas.
The coding taking to get a playable game. Well coding kept me thinking a lot of design and tons of researching. Well I keep it simple. There are many way to make a collision depends on code and graphics. (2D /3D) Build with physic or not that depend on the coding and game play.
The art work and making models takes time out me. The art work comes story or not but it important to make part of the game play. To able to an idea for the goal. But which come first or last is total random.
Well planning or not planning depends on what you can do with your ways.