i DEFINATELY buy wayyyy too much horse stuff..and i dont even have a horse!
i also have a saddle pad addiction which was mentioned above as well..
my biggest thing is that i have a lot of anxiety when i ride. im just a very anxious person and often have anxiety attacks. now that im starting to ride a little more often, it has gotten better. but my trainer really needs to force me and talk me into things i have done and she knows i am capable of doing. i just easily tense up and go into my kind of nervous position (lean forward a bit and play with my reins) this has gotten a million times better, but i still need to work on it at times. once im in the saddle and continue doing things im a lot better though..its the waiting, standing around while another lesson finishes up or even just the walking and waiting for my trainer to tell me its time to trot that really gets to me. recently, i also had a group lesson and i couldnt stand it when i would jump my few jumps, then stand in the middle and wait for the others to jump. i just cant stand the waiting and doing nothing.. i get too antsy i guess you could say haha.
another thing that goes along with the anxiety thing, everything needs to be "perfect" in my mind. my girth needs to be on certain holes, i can not wear a specific pair of breeches, i have a shirt i can not wear, if i wear this one pair of purple socks theres only one shirt i can wear with it, numbers mean a lot, i can only pick up my canter at certain places in the indoor, and my stirrups need to be even and at certain holes - this really got me because since the left one stretches, my trainer finally convinced me to go up a hole, lets just say i thought i was going to die and didnt think i could ride with them like that. the whole night and morning/afternoon before my lesson is also planned out each time i ride in a very specific way. when i just ride myself and hack other peoples horses, this issue isnt as bad as it is for when i lesson.
just a comment on the saddle slidding and tightening your girth thing.. my friend REFUSES to tighten her girth. she will put it on and leave it how it is. one time i checked it for her before she got on (before i knew about this) and could fit both of my fists between her pony and girth with room to spare! i have already seen her get off during rides with the saddle all the way to the side, she will adjust it and maybe tighten it a hole. at the one show this summer, she slid right off the side of her pony during schooling, the saddle ended up under his belly!