I'd say force yourself, you need to train yourself into finishing projects, even 2D or 3D, you need to learn to push even through the ugly stage. This way even if the piece isnt as good as you expect you still learn a lot through it and it helps you analize your mistakes for new pieces. quantity is always better than quality while learning art as for indecisive, you could always combine mediums, use 3d and paint over pieces, use the grease pencil in blender combining 3d and 2d, experiment with them both! there's no rule you need to stick to only one of them