In no particular order:
1) shitass blurple lights overheated my tent to like 100F even with an 8 inch duct fan
2) not sealing my tent with proper HVAC tape - my house smelled like dank weed. Not exactly a problem, but I didn't feel comfortable having guests over.
3) poor water/nutrient management
4) not giving sativa buds enough flower power time
5) too much veg time and wack ass pruning technique - my plants outgrew the tent and trimming buds sucked ass.
I ended up with smokeable decent bud - but it just left me wondering how good it would have been if I did a better job. Essentially, I kept the top buds for myself and sold everything else as shake to friends. It all comes with time