How to avoid uncertainties in prayer

(There are seasonal changes in the shmone-esre prayer. They have to do with rain and dry seasons in the Land of Israel.) It happens quite frequently that at times like these (when we just switched to saying “give dew and rain”), I’m uncertain whether I said the right words during prayer, because I didn’t get used to mentioning rain yet. Because of that, I have to say the prayer over again. Is there anything I can do about it?

Saying the words “give dew and rain” ninety times helps one get used to saying the right insertions in his prayer. This number corresponds to praying three times a day for thirty days. Thus, you should say ninety times “all kinds of crops for the best, and give dew and rain for a blessing on the face of the earth”. After that, if you are uncertain, what exactly you said in your prayer, you’ll be able to rely on this practice and assume that you said the appropriate words. Now you don’t have to go back and say the prayer over again.

Shulchan Oruch, section Orach Chaim, ch. 114, §9