In addition to relentlessly resourceful, you want a tough and a calm cofounder.
As you grow, it feels hopelessly corporate but it really is worth putting in place these compensation bands.
In YC experience, 2 or 3 co-founders seems to be about perfect.
Cofounder relationships are among the most important in the entire company.
Two other things that we hear again and again from our founders, they wish they had done earlier, and that is... simply writing down how you do things and why you do things.
One thing that often disrupts momentum and really shouldn't is competitors.