I think it helps to talk to the kids about how to deal with things when they arent in the middle of it. So talking with them about how to deal with frustration when they are frustrated is not gonna sink in. I would try and find time when your kid is in a good head space and talk to them with how they deal with things when they are really excited, how they deal with when they are scared or nervous and how they deal with things when they are frustrated. Then you can talk about how you handle frustration etc or things they can do to handle it in a way that gets them back to feeling good quicker. I would also point out that frustration is normal and its not about getting over it as quick as you can but more about dealing with it so you dont have to dwell on it. Frustrated is a crappy way to feel so we dont want to feel that way forever.