My experience is that in general they will continue to repeat their instructions over and over again until we get it, but with regards to specific samaya, especially if we have a close relationship with the human emanation of our Guru, it is critical to have a discussion with our Lama about it. It might be that they recommend distancing each others proximity and involvement in order for the disciple to not only purify but to come to clear conclusions and decisions about the trajectory of their behavior. Sometimes the distance may naturally arise and the disciple only returns many years later to a crossroads where they have repaired things inside enough to maintain a decision that was previously broken on a repeated basis. When they reach that plateau and make the decision, it is very important to follow thru. With knowledge and commitments comes responsibility, and the greater the knowledge or more powerful the commitment, the greater the responsibility, and likewise the greater the fall if it is broken once again. That is why it is important to be careful and skillful with our promises. Making determinations to try our best is a very minimum; to keep the intention, for if we abandon the intention to keep the samaya, then it is truly broken!
We definitely need to learn to forgive ourselves, but to embrace our shortcomings while recognizing that we are not our delusions, that we do not have faults but that we have delusions in our continuum and that these have faults. Unfortunately, if we keep making promises or determinations and do not establish the supports to maintain these, not only will we keep falling but we will establish a very strong tendency to repeat the downfall. Therefore, as a basic intention, we need to keep the intention to keep all our samaya. On that basis if we skillfully make determinations that are within our capacity, then strive with great effort in the lamrim, we will be less likely to break it.
For example, I have certain habits that are very detrimental to fulfilling my bodhichitta; that take me in the opposite direction. In the past I would commit for a week at a time but I even broke this. So, I make special promises every single day during a certain sadhana that "from now until my next session of this sadhana, I will not...." Not only have I found this more manageable, but it has enabled me to keep the promise and this has given me encouragement. It has also had a profound impact on my mind, my intentions, my capacity to keep certain important samaya. So being skillful is important.
Though keeping the intention is the foundation, it must not become an excuse for not keeping certain commitments. We'd say shit like "Oh well it isn't my capacity so...". That is true to an extent, but there are certainly things we can keep that we just get lazy with!!
If we definitely believed in karma and future lives; that the realizations were real, and that we are a good person worthy of those attainments, the meaning of saying we will keep the vows and commitments even at the cost of our life takes on a new meaning for us within our own consciousness.
Meditating excessively on the faults of samsara is very important, but it is equally encouraging to meditate excessively on the results of our practice. In particular, if we are moved by the details of commentaries on the 6 stages of completion stage (isolated body and so forth) we will be blown away by what's in store for us if we really apply ourselves. Sometimes just by reading the precise scientific technology those subjects, such as how to attain the deathless vajra body, our mind becomes elevated to a point where we look at some of our actions and daily concerns and go "what the hell am I putting so much effort into all this stuff for?" It doesn't mean we don't engage our world, but our views and intentions begin to change and our priorities change so that we at least include certain trainings every day.
Sorry to go on and on about that, my intent is to show that great effort in actual meditation as frequently as possible is the real key to keeping samaya. We need to taste the realizations and insights in meditation non-conceptually for them to have the deepest impact, but like I said, even conceptual determinations over and over again will begin the process of real transformation. With familiarity we can accomplish anything...its what we pay the most attention to that is our problem!