I am not an expert in this field nor do I claim to be, but in my experience (speaking w boys who have gone OTD, and have come back some totally some semi) I am under the impression that many times it comes from a lack of appreciation for Yiddishkeit and laziness.
If you do not fully appreciate Yiddishkeit and Hash-m why would you want to wake up in the morning and go to Daven? Why would you want to dedicate a whole day of your week to Him? Why would you want to limit your desires because He said so?
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