I read a letter on a religious advice site. The writer reports that her husband stopped putting on tefillin a number of months ago and asked what she should do.
The person who answered suggested that maybe he puts it on at work or elsewhere [and then other avenues were explored]. A person who works as a manager in a hi-tech company with "Charedim" said that a few minutes before shkiya a whole line of people come in to a room to quickly put on tefillin. To quote:
מנהל פרוייקטים באחת מחברות ההייטק סיפר לי, כי כמעט מדי יום נכנסים לחדרו עובדים חרדים ש'מגלגלים תפילין' חמש דקות לפני השקיעה.
This is important to know. It means that leaving the comfortable world of the Yeshiva poses serious challenges to one's ruchniyus.
What the person who answered the letter didn't note is that if tefillin went then it is more than likely that other things were dropped as well. Usually, when someone starts a downward spiral spiritually then it is matters related to sexual purity that go first. Which means that he is probably looking at things on the Internet that he shouldn't, involved in less than 100 percent kosher interactions with women etc. etc. עבירה גוררת עבירה. Also, if this person is just putting on tefillin now chances are that he didn't daven shachris [and of course one may not eat before davening but what do you think the odds are that they all fast daily?].
So for all of us - remember that no matter how much Torah you have studied in life or how many pirkei tehillim you have said, there is an ever present danger of falling really low.
The way to protect yourself is
1] Constantly daven that Hashem protect your soul.
2] Remain very serious about learning.
3] Have a daily schedule that doesn't allow for time to Facebook [unless you have a very good reason to be there] or other cancers.
4] Connect to a Rov/Talmid Chochom/Tzadik. My experience has shown that the boys who remain connected to their rabbeim are infinitely more likely to remain strong [of course that might not only be the cause of their continued growth but also the effect of their desire and resolve to keep growing].