At times, there are certain questions for which we can't find the answers by "logical" thinking; "logical" thinking only works on issues that we face with in this physical world, but then there are certain facets of life which are not bound by the time-space continuum; to find answers to those burning questions we need to explore non-newtonian "sciences" which are not bound by time and space. Astrology is one such aspect of meta-science which acts within the realms of ketheric plane, a plane which is more abstract than the emotional-mental plane. In my life, it's been quite often where it looks like some unknown force is driving my life and I am a mere spectator; for instance: relationships...and quite often, when we are not able to find by mere "logical" thinking itself the reason behind it all, we turn to more abstract ways of finding the answers. Human mind has been trained since time immemorial, to only accept answers which are arrived at by using the laws of inference, observation and exclusion. Now, the question comes, why are people scared of meta-physics (or don't believe in it at all)? Is it because, the laws of inference and observation don't behave well within this realm, or is it because we; humans have been told that we all have free will: will to change anything and everything about who we are and where we're headed? Free will is one aspect which arguably doesn't gel that well will all the "predictive" sciences. I strongly believe that though all the meta-physics are great for finding the "challenges" a person might face in this lifetime, they are often not the right way (actually, there is no other way, either) of predicting the future. Why is that so? Remember, meta-sciences operate on the ketheric plane, but the manifestation of those events happen on the physical plane and quite a few things are lost in the translation (free will, anyone?). Does it mean, we can change everything about us, defy everything written in the stars? No, free will only can change the way you allow yourself to percieve those events and their manifestation, life is all about perspective: what a caterpillar calls the end of the world, the master calls a butterfly!
Coming back to the law of relationships as per the stars, the things to look in a natal chart for relationship promise is to look at position and strength (using Ptolemy's dignity) of venus, moon and their aspects with any outer planets.
I have a libran (ruled by venus) ascendant and venus becomes the chart ruler (i.e. venus becomes quite prominent in defining who I am and hence, all things venusians become quite significant to me). Venus is only dignified by face in Aquarius and is conjunct by Sun (Sun: I, the very being, the ego) Since, Sun and venus are conjunct; they are fused together and act as one and now again, who I am is greatly defined by venus (Sun in aquarius being debilitated, I'd say Venus "wins" between the two planets). Also, since Venus is in the fourth house, it means these are aspects of my life which are not very apparent to others, they are buried deep down inside and very few will have a glimpse of this side of me. Now comes the moon; moon is all thing feminine, our emotions, our ability to feel safe in a relationship, our feeling of nurturing and being nurtured. I have moon in scorpio (in fall), in the first house. Having a first house scorpio moon means emotions play a good part in my life: also scorpio moon has this uncanny knack of reliving the painful past, till it conquers all the demons. My moon in scorpio "squares" venus in aquarius: a quite "challenging" aspect, which means these two energies act at cross-purposes to each other, which kind of explains why sometimes, I had this feeling of being "unsafe" in the relationship. Coming to outer planets (uranus to pluto); anytime there is an aspect between the outer planets and the moon or venus, you can expect some drama; how the drama is going to unfolds depends on the kind of aspect: easy (trine, sextile) or challenging (square, opposition, conjunction or inconjunct). I have uranus (planet of surprises and unexpected events) conjunct my moon and squaring my venus. Uranus is a sudden flash of lightning, which seems to strike almost unexpectedly and lead you to completely unchartered waters. Uranus, moon conjunction means there will be quite few sudden interruptions in one's ability to feel safe and so will be one's emotional ups and downs; and uranus-venus square means again sudden and unexpected interruptions in a relationship (you bet!). I have a sextile between neptune and venus, making one very dreamy and imaginative in a relationship: someone who is a true romantic at heart (sextiles are dormant aspects, they need to be activated). I also have a trine between pluto and venus, which means relationships will play a big part in ones "transformation" (since it's a trine: I guess the transformation has to be for the good) and also suggests certain power issues in a relationship. Since, we are it; I also have Chiron (the wounded healer) in my seventh house (house of serious one-one relationships); anywhere you find Chiron in the chart, you can be pretty sure that's one aspect of your life where you will face most of your "lessons", so no doubt, everything that I've learnt in my life has always involved a partner.