I feel like whatever I transfer to Adobe Illustrator is loosing the concept's original features?

I can draw pretty cute thing that in my imagination would look good in vector format. But I'm just plain frustrated whenever I need to work with Adobe Illustrator and transfer my thoughts on digital 'paper'. Lines break when I click 'unite' in pathfinder, proportions are out from original, I need to deal with kinda different color feeling and often 'debug' rather than 'compose' type of workflow. How can I change it ? How can I become better ?