Why the specified moment does the work
Two things sitting together. The report below attaches the easing to the one who treads the path, not to the one who intends to tread it, which is the point of this lesson stated in five words. And the research on if then sentences is good, with limits its own authors name.
Qur’an and Sunnah
فَتَعَٰلَى ٱللَّهُ ٱلۡمَلِكُ ٱلۡحَقُّۗ وَلَا تَعۡجَلۡ بِٱلۡقُرۡءَانِ مِن قَبۡلِ أَن يُقۡضَىٰٓ إِلَيۡكَ وَحۡيُهُۥۖ وَقُل رَّبِّ زِدۡنِي عِلۡمࣰ ا
exalted be God, the one who is truly in control. [Prophet], do not rush to recite before the revelation is fully complete but say, ‘Lord, increase me in knowledge!’
Qur’an 20:114
Abu Huraira reported Allah's Messenger (ﷺ) as saying:He who alleviates the suffering of a brother out of the sufferings of the world, Allah would alleviate his suffering from the sufferings of the Day of Resurrection, and he who finds relief for one who is hard-pressed, Allah would make things easy for him in the Hereafter, and he who conceals (the faults) of a Muslim, Allah would conceal his faults in the world and in the Hereafter. Allah is at the back of a servant so long as the servant is at the back of his brother, and he who treads the path in search of knowledge, Allah would make that path easy, leading to Paradise for him and those persons who assemble in the house among the houses of Allah (mosques) and recite the Book of Allah and they learn and teach the Qur'an (among themselves) there would descend upon them tranquility and mercy would cover them and the angels would surround them and Allah mentions them in the presence of those near Him, and he who is slow-paced in doing good deeds, his (high) lineage does not make him go ahead
Sahih Muslim 2699graded sound, sahihaynfull report
Translation: M.A.S. Abdel Haleem, The Qur'an, Oxford University Press, 2004.
What the research says
Gollwitzer PM, Sheeran P (2006). Implementation intentions and goal achievement: a meta-analysis of effects and processes. Advances in Experimental Social Psychology, 38, 69 to 119 doi
A pooling of a large number of tests of if then plans. Specifying when and where you will act, on top of simply intending to act, improved whether people actually did the thing, and the improvement was substantial. The authors flag their own limits: concerns about publication bias, and evidence that these plans help much less when the underlying goal is one you do not really hold.