You'll lose the most time on the rough edges of each thing, the one or two minor things you didn't get around to solving on each effectively stack as the pieces

You'll lose the most time on the rough edges of each thing, the one or two minor things you didn't get around to solving on each effectively stack as the pieces are expected to work together. It's like multiplying probabilities, even though each is 95 - 98 % done, the whole is like 40% done when there are many pieces like this. This has a terrible effect on morale since it presents as insurmountable.