Rather than expecting ideal circumstances, plan for the worst. Rather than underestimating how much time and effort something will take, overestimate those things
Tell Me What You Did Today, And I’ll Tell You Who You Are
Benjamin P. Hardy

The beauty in 'overestimation' of delivery time lies in ‘over achievement’. The self-awareness that comes with planning for the worst spurs focus and intent.

This translates to accelerated growth and swift achievement of targets.