So this theory could make sense. Some practical advice: don't take it too hard on yourself. If someone says you're slow without backing this claim with data and

So this theory could make sense. Some practical advice: don't take it too hard on yourself. If someone says you're slow without backing this claim with data and/or comparisons, you're slow compared to what? Taking into account the startup context, I'd be hardly surprised if they were just trying to make you overwork.