Q. I heard that there are those who maintain that it is a greater sin the first time one does it (the sin), but when one becomes used to it, the sin is less (naase loi keheter) and others disagree and say the opposite. When time and effort is limited, what is Rav Shloimo’s opinion as to on what should one do teshuva first, on aveiros he is used to do constantly or on the ones he just did a few times?

A. Indeed Meshech Chochmo (Vayikro 5: 11) explains the saying in Talmud (Yuma 86b) “One who transgresses a sin repeatedly, it becomes to him as a permitted act,” that the meaning is to be lenient on the one who continually commits the same sin, since it looses its severity and in his mind it has become the norm and he does not feel he is doing any wrong. A sin that has become common is regarded with clemency since it is now viewed as an accidental involuntary action, as opposed to a first time transgression that is seen as a far more grievous and severe act. (see Pirkey Machshovo ibid.and similar opinion in Yitav Leiv P. Vayehi).
However most opinions follow the reverse reasoning and maintain that an offense endlessly repeated by the sheer volume of transgressions involved is far more severe. (Sefer Hamakne – Kidushin 20a, Maharal – Chidushei Hagodos – Eiruchin 30b, Liflagos Reuben 2: p.219, et. al.).
Horav Shlomo Miller’s Shlit’a opinion is that in principle one should try to stop and repent on an offense incessantly repeated first. The Rov pointed to a similar position in Sharei Teshuva (Shaar Horishon Ikar Hasheni) and the beginning of Yesod Hateshuva,
However, there are usually many other factors to be considered and the chozer bitshuva should privately consult with his Rabbi, mentor or capable friend.

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit’a