Thanks to all of us for your tips !
I will try !
Rikkie: I have this horse since two weeks !
Just start with a soft brush to their entire body, give them a cookie if they behave, and then try the same thing the next day but brush their mane and reward if she doesn't do anything stupid.
Try to find his/her favorite spot to be groomed/scratched. For example, my horse loves it when I itch her mane. If you find a sweet spot, stick with that spot for a while to make them enjoy standing and being pampered
How long have you had this horse?
I would try maybe first starting with your hands and petting him as you would grooming. Then go from that to a soft brush and then advance from there. Get him used to that contact and ease him in to get him to relax.
What worked for me was just grooming them every day to get them used to it. Also rewards help a lot. Just curry or brush them and if they don't nip or move, give them a little animal cracker or somethin