A really interesting question, DragonsFriend- and one which I haven't been able to satisfactorily answer myself thus far. That said, it's something that's really pertinent to me because I struggle with the fatalism vs indeterminism (is that even a word? No words came readily to mind for fatalism's opposite) question a lot in my dealings with divination.
I come from a culture where astrology is very much a part of daily life- especially when it comes to things like marriages or starting new business ventures. Basically, you wouldn't consult astrology to figure out how your week's going to go...but if you're getting hitched or starting a new venture, you probably might. It isn't exactly belief so much as a niggling worry at the back of your mind.
I don't know if- but am sure it probably does- western astrology operates from the same paradigm that eastern astrology does, but over here your natal charts can
theoretically map out your entire life...down to the gender and number of your grandchildren (!)....and the celestial bodies (the Sanskrit word
graha is used for planets, moons and starts as well) are taken as the
only factors affecting your life....your personal ability to affect changes in the wyrd (I love the conception of the wyrd- the imagery makes so much sense!) is non-existent or goes un-acknowledged.
So a period of ill-dignified Mercury (I'm totally making this example up, please don't kill me

) in your life isn't about facing challenges in communication so much as a period of everything communication related going wrong in your life- do you see the difference in perspective?
What disturbs me even further is how prospective spouses are astrologically evaluated for compatibility.
Depending on the time and place of birth (basically, which stars you were born under) a person can be
Manav (Human),
Dev (God) or
Rakshash (Demon)*: the groups are somewhat like personality types.
(Interesting tidbit... a
Dev or a
Rakshash is usually very easy to spot from their personality)
You have rules which dictate how compatible these groups are with each other: M-M, D-D, R-R usually get along fine, as does M-D. D-R couples usually are too busy fighting to make a relationship work whereas, and here's the kicker, M-R matches are forbidden because the M half of the couple generally gets killed before their time.

Something in me really, really bristles at the idea that two different kinds of people will somehow "magically" invite influences into their lives which will result in this kind of a tragedy...no, just no.
Evaluating how well two people will get along based on their natures is something I understand- I can do similar things with the Tarot- but I just can't get myself to accept that someone's nature can "invite" tragic circumstances like an untimely passage.
That said, since this is one of those nebulous, boogeyman sort of things...I can't completely forget it either. Like I said, a niggling worry at the back of my head.
On the whole, I think I'm most inclined to agree with Tirya ATM...it would be hubris to say I'm the only one in control of what happens to me...but at the same time, I do get to have a pretty substantial say in what happens around me.
(By "me", of course, I mean generic me...being on the path of mysticism just means I might have a certain kind of arsenal at my disposal to affect changes; someone who isn't into mysticism might have another equally valid kind of arsenal)
*there really isn't an English equivalent for the Sanskrit words rakshash, daitya, asur etc. We use the word demon to translate it because they were frequently at odds with the people who worshipped the Vedic deities; but they were not unholy cast-offs like Abrahamic demons. Many asurs were ardent devotees of some God of the pantheon, and frequently came by their powers by pleasing the Gods.
Anthropologically, they are probably how the tribal, fringe populations were remembered by the so-called "civilised" vedic peoples since there must have been racial/cultural skirmishes The asurs represented threats to the Vedic way of life but were definitely not considered any less worthy of worshiping the GodsTL;DRPersonal power is a concept that I do struggle with often. From the meek, victimised attitude to the arrogant, "master of my/the universe" one...it's a sliding spectrum for me.