And embrace the fact that essentially, you will be looking after and cleaning a half a ton toddler for a few decades. Especially when you have to clean poo off their bum for a show.
Whether you have enough money available to pay for everything - including that 'final decision' (did you win the lottery )
That every yard has at least one person who knows better than you/the vet/farrier etc but is really 'all the gear but no idea'
That there will always be people who will criticise every thing you do and voice their opinions loudly. The answer to this is "if I wanted your opinion I would have kicked your kennel"
That there are 'horse' people who will go to the ends of the earth to help you no matter what.
That a horse can be your best friend, who understands when you are feeling down and will be the one reason you get up in the morning.
That despite knowing how expensive/time consuming/demanding having a horse can be - you will probably do it anyway and whist complaining about it wouldn't change it for the world
Getting the right horse IMO is the key to how easy or otherwise your life and enjoyment will be. Get the wrong horse and everything can be a battle, get the right one and everything is nice and so much easier. Ensure the horse does everything willingly including the basics like standing for the farrier or loading and travelling nicely etc. Having had my share of slightly challenging horses (Ive never had a really awful one thankfully) I really appreciate it when I have a horse who is a dream like my current one. Temperament is everything IMO.