Sometimes you can be “cold” to men in general, when you simply feel like being alone.
But if you’re looking to have a “cold heart,” then you’re probably trying to get out of an unhealthy relationship with a romantic partner or family member.
To do this, you need to be absolutely sure that you are closing yourself off to the person emotionally and physically. You also need to keep reminding yourself why “cooling down” is a necessary but temporary measure to regain control of your life.
1. Make your decision and stick to it.
Once you’ve decided to become cold towards someone, you must remain firm in your decision to do so. Keep reminding yourself why it is critical to your own well-being and happiness that you cut ties and close your affection for this person.
Be very clear when breaking up: “I realized this relationship is bad for me and I decided we can’t be together anymore. This is non-negotiable.”
Cutting ties this way is a difficult and challenging move, so save it for cases where a relationship is clearly bad and can’t be repaired.
2. Cut contact as much as possible.
If possible, do not accept phone calls, emails, Facebook messages, etc. Every time you give them a chance to explain or apologize, your resolve can be weakened.
Explain the change one and only once: “I don’t want us to have any contact unless it’s absolutely necessary.”
You should view each and every attempt at reconciliation as the other person’s desire to put him back in the position of hurting you again.
3. Keep any communication with him as short as possible.
When forced to talk to the person, use “no” as a full sentence if he asks if he can call you, if you can explain things, and so on.
Tell him your boundaries clearly so he understands that you don’t want to be involved anymore.  Otherwise, give short, direct answers such as “I can’t”, “That’s not possible”, or “I don’t have time for that”. Then walk away, hang up, etc. 
Either pretend not to notice or not hear him.
Use these tactics when dealing with a coworker or classmate, for example.
4. Don’t reveal what you’re thinking or feeling.
Don’t express anything that could be interpreted as doubt or remorse, like saying “sorry,” whether you like it or not. Do not show signs of permanent affection. Don’t even look in your direction. Close completely.
Don’t get caught up in arguments about how you’re going to move forward, what you plan to do next, and so on. Become a complete mystery to him.
You have already expressed your decision to him. You don’t owe him anything more than that, no matter what you say.
5. Refuse to remember the feeling you had with him.
Don’t think about the “good times” you may have shared. You can’t be cold hearted while you have good memories. Delete all texts, emails, etc. Get rid of photos, gifts, and anything that reminds you of them.
Even if you had a good time, your memories of those times must be sacrificed in order to get rid of this person.
Perhaps in the future, after getting into a healthy relationship, you will be able to safely remember some of those “good times”.
6. Remember that you are powerful and in control.
Thanks to brain chemistry and social reinforcement, people in positions of power or control are less able to empathize with others. And it turns out that even a temporary “power trip” diminishes your ability to “feel the pain” of others.
To explore this element of human nature, keep visualizing the moments in your life when you felt most powerful or in control.
For example, before any situation you might encounter someone else, remember that you built a successful business from the ground up, that you secured your financial future, or that you earned the respect of the people around you.
7. Remember why the relationship had to end.
When you become weak in your decision to be cold-hearted, you will find that anger is a very good motivator.
When times get tough and you’re tempted to give up, get angry. Remember all the times you were bullied, lied to, or left without the support you needed.
Write a detailed list of all the ways the person has hurt or let you down, and refer back to them as needed. Or, if it helps, stick their picture on your dartboard or punching bag and go for it.
8. Keep yourself busy with other activities.
It is important to occupy your mind and keep yourself occupied during this transition period. Start a new hobby you’ve always wanted to try, or go back to doing something you used to enjoy.
If certain activities or hobbies remind you too much of the person you’ve become insensitive to, stop doing those things at least for a while.
Or change the conditions – join a new gym, take an art class instead of a cooking class, etc.
9. Rebuild relationships with loved ones who support you.
If the challenges of the bad relationship you were in have damaged your connections with others, strive to be a good friend, sister, mother, etc.
Show the loved ones who have been by your side all along that you appreciate their support, support.
Don’t let your cold heart reach out to them.
Show them the loving warmth they deserve!
10. Create a strong self-care routine.
Make good use of all the time, attention, and affection you’ve taken away from the other person, focusing on yourself. Prioritizing your own needs will help give you the emotional and physical strength to keep the clean breakup you made from a harmful relationship. Focus on:
Physical health – exercising regularly, getting enough sleep, following a healthy diet.
Emotional care – meditation, prayer, yoga, tai chi, relaxation exercises and so on.
Spend time with friends and family who support you.
Doing things you enjoy – going to the movies, going out, traveling, etc.
11. Seek additional help if you need it.
Ending a relationship, even with an “emotional vampire” who receives without giving in return, is never easy. If you are not able to turn with a cold heart to the person and let go completely, there is no shame in seeking help.
Get referrals from your doctor or friends and family to licensed therapists in your area.
Working with a therapist can reveal that trying to be “cold” for a while is not the best option for you. The important thing is to find what works best for you.
12. Don’t be cold towards the world.
Remember that you are choosing to be cold-hearted in a specific way for a specific goal.
You have the power and control over the situation. Once you reach your goal of breaking free from a harmful relationship, go back to what you were before.
People who are naturally cold-hearted often have an “avoidant attachment pattern” that developed during childhood.
So being temporarily cold for a specific purpose doesn’t have to make it permanent.
But if your coldhearted turn is successful, you might be tempted to use it more often or more widely. In that case, remember that isolating yourself from the world will cause more pain than it will prevent.