Wonderful post and question, DS Friend.
What is stopping us?
No simple answer but it is a ceaseless accumulation of bad karma, lack of merits, wrong views, inner and outer obstacles from life to life, ignorance, and etc. All these combined and more would be enough to kill us off at any point in time.
Unlike the Victorious Ones - each of their lifetime have been dedicated wholly to Dharma and the pursuit of Attainments, Realizations and Enlightenments. They have reinforced everything they have learnt, retained them and made real efforts to come back with the memories of these attainments life after life.
Hence, the Victorious Ones are totally in control of their birth, rebirth and etc.
We can't even control our impatience, let alone anything else.
So, how can we change the course of our seemingly samsaric bound life after life?
We make a real commitment to do things differently from here on, NOW.
We start by creating new habits, new causes for us to be able to meet our Guru and the Dharma again - life after life.
We may not gain much realizations in this one lifetime, but we definitely will make real progress that will become the basis for our next life to be much better. And build further from there, from one life to the next.
If we are truly dedicated and diligent, who knows, we might be the lucky few to gain attainments in one single lifetime.
Anything is possible. Nothing is set in stone. We can change our destiny, if we put in the right methods and dedication.