We might not know we are seeking people who best enrich our lives, but somehow on a deep subconscious level we absolutely are. Whether the bond is temporary or permanent, whether it succeeds or fails, fate is simply a configuration of choices that combine with others to shape the relationships that surround us. We cannot choose our family, but we can choose our friends, and we sometimes, before we even meet them.
Plainly it isn't an exact science, despite it being a complex interaction of micro-decisions and corresponding thought; perhaps it doesn't always work and we pass by some potential soulmates like the proverbial ships in the night, never quite connecting. Then again, perhaps the system is tenacious and continues to run like a computer program on infinite loop, so that if at first you don't meet, you are drawn back together for another try.