There is a statement in Moed Katan (28a) made by Rava. It says (Translations are Soncino):
"Rava said, 'The length of a person's life, the number of his children and the extent of his sustenance is not dependent upon his merit, rather it is dependent upon his mazal (fortune). [This must be the case] because both Rabbah and Rav Chisda were righteous Rabbis as is evident from the fact that if either would pray for rain then the rain would fall. However, Rav Chisda lived nintey-two years whereas Rabbah lived only forty. Rav Chisda's household celebrated sixty weddings whereas Rabbah's household suffered sixty tragedies. Furthermore, Rav Chisda's household fed bread of fine flour to their dogs and it was not needed whereas Rabbah's family ate bread of barely flour and there was never enough.'"This passage from the Talmud seems to tell us that nothing is within our own power, rather everything is determined through natural means, only when great individuals pray does G-D intervene. This means that everything is already determined from our "fortune." In light of this, even the Ralbag's idea of extremely holy and righteous people being under a divine watch would contradict Rava because according to his opinion there is no divine intervention unless the extremely righteous person prays for intervention. However, Rava continues with the following qualifying statements:
"Rava said, 'For these three things I entreated heaven, two were given to me and one was not. I asked for the wisdom of Rav Huna and the wealth of Rav Chisda and they were both given to me.'"The Maharsha tells us that this shows us that even though Rava is of the opinion that everything is from one's "fortune" a righteous and holy person can still entreat G-D and be answered. On the surface, this seems like what was already made known previously in the Gemara when it says Rav Chisda and Rabbah were able to pray for rain. However, that revealed that G-D would grant requests for specific interventions. A righteous person asks for rain then he will receive rain. However, Rava asked for more than just a singular action, Rava asked for wisdom and wealth. Wisdom and wealth are not things that just pop into existence in one instance and stay, they are things that can come and go. It is only through G-D's constant intervention that a person who receives money will be able to retain that money. The same principle goes for wisdom. In essence, there is hashgacha pratis for holy and righteous people.
This idea is also seen in another part of the Gemara (Shabbos 156b) where it points out cases where righteous individuals are able to overcome their "fate" because of their righteousness, not even entreating G-D. The two stories are:
"From Samuel too [we learn that] Israel is immune from planetary influence. For Samuel and Ablat were sitting, while certain people were going to a lake. Said Ablat to Samuel: 'That man is going but will not return, [for] a snake will bite him and he will die.' 'If he is an Israelite,' replied Samuel. 'he will go and return.' While they were sitting he went and returned. [Thereupon] Ablat arose and threw off his [the man's] knapsack, [and] found a snake therein cut up and lying in two pieces — Said Samuel to him, 'What did you do?' 'Every day we pooled our bread and ate it; but to-day one of us had no bread, and he was ashamed. Said I to them, "I will go and collect [the bread]". When I came to him, I pretended to take [bread] from him, so that he should not be ashamed.' 'You have done a good deed,' said he to him. Then Samuel went out and lectured: But charity delivereth from death; and [this does not mean] from an unnatural death, but from death itself.These stories point out the ability for one to overcome their "fortune" if they are righteous. In Shmuel's case the man was saved through his act of charity and in Rabbi Akiva's daughter's case there is a similar idea.
From R. Akiba too [we learn that] Israel is free from planetary influence. For R. Akiba had a daughter. Now, astrologers told him, On the day she enters the bridal chamber a snake will bite her and she will die. He was very worried about this. On that day [of her marriage] she took a brooch [and] stuck it into the wall and by chance it penetrated [sank] into the eye of a serpent. The following morning, when she took it out, the snake came trailing after it. 'What did you do?' her father asked her. 'A poor man came to our door in the evening.' she replied, 'and everybody was busy at the banquet, and there was none to attend to him. So I took the portion which was given to me and gave it to him. 'You have done a good deed,' said he to her. Thereupon R. Akiba went out and lectured: 'But charity delivereth from death': and not [merely] from an unnatural death, but from death itself.
In the end of the day it seems like the Gemara is telling us how G-D runs the world. It tells us that the world runs through nature (planetary influence here). This is why bad things happen to good people, like by Rabbah being poor and dying early. It would appear to be that he did not ask for divine intervention and that is why he lived in poverty and the like However, Israel has the ability to change these natural occurrences, through doing mitzvos and connecting to G-D.
For a related post as to how G-D might interact with the world see here: http://markset565.blogspot.com/2011/02/how-does-g-d-work-in-this-world.html