To sum up the point, if you 'have'
to do something such as getting a serve in it might cause unintended tension to soon develop in some of your muscles. Perhaps that tension is what screws up your serve (and also many clutch serves of ATP and WTA players).
Alexander - as I understand it - if he were serving, might have said to himself 'I don't
have to get this serve in'. Actually saying this would prevent his auto sequence of muscle tightening and relax him.
The next time that you are serving at 5-4 for the match tell yourself that you 'don't have to hold your serve'.........