get his teeth checked. Make sure there are no abnormalities/abscesses and make sure they are floated on time. Water is a big one too, if the water is too cold where you are they are less inclined to drink so make sure he has a salt block. If he does have a severe enough wave in his teeth or if he is missing teeth fk inhibit proper chewing/breakdown of the hay stems then go to soaking hay cubes in a generous amount of water instead of solid hay. Get him on probiotics and a gastrointestinal supplement.
Make sure your horse hasn’t gastric ulcer or eating disorders. The environment should be as stress free as possible. Try to reduce grain and similar and substitute them with high quality fiber. Make small portions and let your horse walk a lot. Do a good warm up and cold down after working and never leave it wet after training or showers especially under the belly and over the kidneys.
Ask your vet to check out for behaviour disorders and gastrointestinal medical conditions
Some horses are just more susceptible to colic. It would help if you could figure out why. But doing a bit of research on colic might help so you can use preventive measures to stop it happening again.
Try not to turn out in a sand arena, don't feed large meals, leave a good space between feeding and riding, keep him fit if possible and no sudden changes in routine. But I have heard that some horses react to change in weather badly so if you could keep him in at night that might help