There are so many reasons why this is bad.
It boils down to boundaries. Having blurred boundaries with an ex, or in general, can mess up a good thing or prevent you from getting into a good thing.
People in unhealthy relationships or those who seem to find themselves in bad relationships often have blurry boundaries in general and that includes staying too close to exes and others who aren't good for them. When you strengthen your boundaries overall, your relationships become better in all areas of your life.
An ex is an ex for a reason. Even if your ex-boyfriend or ex-husband is a great guy, you should focus on meeting other men. Frankly, I see too many women clinging to exes—who were bad for them—for low-level reasons, including for financial perks, a shoulder to cry on, and help when they get into an emergency situation, like a car accident. That's what AAA is for. That's what family, friends, neighbors, support groups, etc. etc. etc., are for.
And there's no reason for a woman to ever give an ex a gift for a holiday or any other occasion. Unless you're divorced and you have a 5-year-old child together, for example, and your child wants to give "daddy" a Father's Day (or whatever holiday) gift. You should buy a gift so your 5-year-old can give his father a gift. Beyond that, gift giving to an ex is extremely unhealthy and dysfunctional and evidence of very poor boundaries. Plus, masculine men don't want gifts, especially from ex-es. (More on gift giving in another blog).
This isn't to say you're nasty to your ex. If you have to be in touch, you have to be in touch, but keep it at a surface level. You may need to stay in touch because of your children, or due to professional or other reasons, but even in those cases, be cordial, but that's it.
If you're having problems with your current boyfriend, the last person on earth you should be talking to is your ex-boyfriend or ex-husband. If you're doing this, it means you need new and better friends.
If your ex is happy and in love, leave him be. It’s bad karma to mess with a man who’s taken. If he's a healthy guy who has moved on and is in a healthy relationship, he'll be happy you're leaving him alone.
And if he’s the type of guy who has a weak ego that needs to be fed by weird drama, stay away. If he's one of those messed-up guys who loves messed-up relationships, you may be feeding his sick ego by staying in his life, and he may be using your calls and presence in a sick attempt to make his current girlfriend or wife jealous.
Former or latter, you don't want any part of either scenario. You have your own beautiful life to focus on.
Some clients have asked me what to say to an ex when they run into him at work or elsewhere. These women don't have children in common or professional reasons to be in touch, but they wonder if they should be polite. If he was a decent guy who treated you well, you can be polite and cordial, of course. But if the guy turned out to be a creep, steer clear. He doesn't deserve a second of your precious time. Don't squander the sexy!