I think my biggest regret was my all-consuming desire to earn influence. Farming for purples and such certainly helped me reach my goal of 100 billion inf (thanks in part to some of those incredible zero to 2 billion inf guides that showed market savvy). However, I never did finish the water power blaster, nor the plant controller, and I really wanted to give my kin scrapper one more try after reaching the conclusion that they were no fun and more squishy than my blasters.
In the end, I just tell myself I didn't lose, I just ran out of time.