We don't need to Hope the sun will come up tomorrow. That probability is 100%. The probability that the outpatient surgery you've scheduled next week will be successful is high. The surgeon has done this procedure 1,000's of time with a 98% success rate.
The probability that you'll be able to arrive on time with the needed features for the first release of the accounts payable and accounts receivable upgrade to the ERP system, is not like the sun coming up or the outpatient surgery. It's actually a probability that you'll have to think about. Actually have to calculate. Actually make an estimate of this probability before those paying for your work can make a decision about when to switch from the old system to the new system.
Hoping we can show up when needed is not a strategy. To show up on time, and on budget, with the needed capabilities. To do that, we need a Closed Loop Control System, in which we have a target performance, measures of actual performance, compared to estimates of the planned performance to create an error signal to take corrective actions.