Its like any relationship, sometimes its "love at first sight", sometimes it takes months or years to build a partnership, and sometimes two personalities just don't get along. If we are talking about the magical black stallion bond(pile of rubbish), then I whole heartedly agree with this:
The whole concept of only by clicking with a horse can you have a safe horse or trusting horse is fairy dust.
you don't magically "connect" with a horse and suddenly they love and want to protect you, no more than "love at first sight" will instantly give you a loving and fulfilling marriage for the next 50 years. All relationships are a lot of work. ALL.
that said, I have had a few horses I really get along with, I have ridden and worked with dozens and they all did what I asked. There was no "muffy doesn't like me, so she bucks me off". they were expected to work and they did it. sometimes we genuinely disliked each other, but they still had to follow the same rules.
Of the horses I have felt the closest connection to, Pickles was instant. she chose me, out in the pasture. Instantly we got along. shortly there after she had a miserable stage where I questioned my decision, but in the end the first impressions were correct(after a lot of WORK, seeing a pattern here?)
my first "love" was sparky. I loved him the day he was born. we got along great from day 1. he died as a yearling, so I really cant say how he was under saddle, but we were great together.
then there is Pretzl. NOT love at first sight. I thought she was the ugliest Arabian I'd ever seen in my life, but she was cheap, sound, and not crazy. It was months later, whipping through a narrow trail at a gallop, that I realized we made a great team. she is not lovey-dovey, and never will be, but we have come to an agreement and enjoy each others company.
some horses I've known since birth and it has taken years to really "connect". One of my biggest pet peeves is the buyer that has seen 20 horses, comes out to see one I have for sale, and tells me, "sorry, but we just don't click", despite being perfectly suited, after 10 minutes of riding. I honestly believe that the majority of great horse/human partnerships take a ton of work, and even in the unusual circumstance of having that instant "connection", you still have to work at it every day.