You can move on. You will move on. It will take time. But you can speed up the process. There are things you can do. Certain ways of thinking and acting are holding you back. Other ways of thinking and acting can help you move forward. You may be ambivalent about letting go of some of the things you are doing that are holding you back. There may be pleasures associated with these behaviors. Having dinner with him, for instance, may have felt good in certain ways. But it was an indulgence you could ill afford. It set you back.
But if you want to move forward, you can. There are things you can do. You can harden yourself with the facts. Get the facts in your head. Hammer them in there. Say these things to yourself: He is not coming back. This thing is over. He is the ex. He is gone. That relationship is in the past. He has moved on. You don't need him. You made the right decision. You were smart to break up with him. You had the courage and the intelligence to do the right thing, in spite of how hard it was. What he's doing now is of no concern to you.
As you try to cleanse your mind of him, also cleanse your house. Whatever keepsakes you have around the house, get rid of them. Do not know his phone number. If his phone number is programmed into your cellphone, delete it. If his picture is displayed in your house, put it away somewhere. (If in cleaning the house you find yourself pausing with keepsakes, stop it! Don't pause to remember! Just put it away!) Do not discuss him with friends. Refuse to learn anything about his new girlfriend. Do not picture her in his car. Do not picture her at all. Do not picture either one of them. Banish him from your mind. Do it forcefully.
You will be happier once you do this.
But you may encounter resistance from yourself. After all, you are waging an internal struggle. So if you find yourself unable to stop thinking about him or imagining the future with him, try this: Sit quietly somewhere, when you have an hour or so of spare time. Perhaps when you are lying in bed about to go to sleep, or in the afternoon sitting in a park, or in the morning with coffee, or -- I don't know when, why am I suggesting times? That isn't important! What is important is that you consider carefully the content of each thought you have concerning this boyfriend.
What do you feel when you think about having broken up with him? Do you feel regret? That's OK. You can feel regret. It doesn't mean you have to change it. It's done. You may regret your decision. But it is a material fact: You are broken up. It is over. He is not coming back. He is an ex-boyfriend. Feel the regret. But know that it's done. Embrace these phenomena independently. See how different they are. One is something you do yourself, within yourself. The other is external, done, beyond anyone's control.
Consider also the habitual ways in which you refer to him. If we are having trouble accepting a fact, sometimes we find ways of not saying it. Do you refer to him as your ex-boyfriend, or do you talk around that fact? Make sure in your habits of speech that you say the truth: He is your ex-boyfriend. If someone asks, say you are glad you did what you did, even though it has at times been hard. Do not go into detail. Do not rehearse the emotions you have. Let them die out.
You also say, "I can't help remembering our vacations, our travels and how happy (I think) I was with him." Let me suggest to you that even if you believe your are powerless over these memories, try to exercise some control over them. Refuse to luxuriate in them. When you find yourself remembering those times with pleasure, stop. Don't do it. Turn your thoughts to something else.
And above all, if you should find yourself thinking about having dinner with him again any time soon, douse your head in ice water. Dinner with your ex is needless torture. Don't do it. Just don't do it.
