even if you were to be "slow and careful" that doesn't garuntee you'll be on schedule, it could turn out later part of your architecture is not suitable for an

even if you were to be "slow and careful" that doesn't garuntee you'll be on schedule, it could turn out later part of your architecture is not suitable for an area maybe due to requirements changing. maybe you'll say, "requirements cant change!" on top of the earlier "deadlines should be reasonable!". IMHO that's fantasy, I've never worked on something where both these were true for 100% of a project