Texting my ex

It's been about a month since we've last talked and it ended horribly. I miss him so much and I saw him around town today for the first time since we broke up. I just want to text him & let him know that I'm happy for him, since his life seems to be turning around. I don't want to get back together or anything of that nature, I just feel bad about how everything ended and want to make amends for that atleast. Bad idea?