If you want to be able to get used to the cold, you’ll have to actually get out in it. If it’s late fall or winter, or if you live in an area with a year-round cold climate, spend a couple hours outside every day. Only wear as much warm clothing as necessary, and shed layers once you get more comfortable. With time, you’ll be be able to spend longer and longer outside and be affected less by the temperature.  When spending long durations outside, try wearing gloves, boots and a hat, but leaving the jackets inside. It’s usually the extremities that get cold quickest, and number fingers or ears might make you call it quits long before the rest of your body actually gets too cold.  Try driving around without the heat on in your car when you have to get out. For more of a challenge, roll the windows down. Turn the shower faucet opposite the direction that you’re used to when taking your daily shower. Taking cold showers can be supremely uncomfortable, but it’s a good head-first way to begin building up the body’s tolerance to immersion in cold temperatures, and it’s the closest many of us are likely to get to the practices like Arctic Sea diving that help bodies begin to make physiological adaptations to cold.  Build up to cold showers by decreasing the temperatures that you’re used to bathing in a little at a time. If you try to go too cold too soon, you may not be able to withstand an entire shower. You might also try alternating between hot and cold water when showering to get used to rapid changes in temperature similar to when you step outside. The function of the body’s fat stores is to provide a steady supply of calories to burn for energy, and to act as cushioning layer to protect and keep the body’s internal organs at a consistent temperature. While not necessarily an attractive option, gaining body fat will keep you that much warmer when conditions are frigid.  Putting on a little extra body fat should be done with discretion; you should still aim to eat a balanced, healthy diet, just with a moderate...

TL;DR in Indonesian:
Keluar dari rumah dan rasakan udara dingin. Mandi dengan air dingin. Naikkan berat badan. Berolahragalah secara teratur.