The following is the answer to a question I posed to Sheikh Walead Mosaad
Q: What kind of yaqeen am I supposed to have when making du’a generally?
And particularly for seeking shifa?
A: Yaqeen that Allah hears your dua and will answer it – but in a manner of His choosing and at a time of His choosing – whether in this life or the next, or by what you have asked for, or something better. So the certainty that the best outcome is chosen and determined by the Best of Planners.