Reinforcing your successes is an important part of solidifying new habits. Tell yourself that you'll treat yourself only if you talk to this specific person, or have a nice conversation with a stranger. Sometimes it is not as easy to be social. This is when a friend can help. A more social friend or even a family member can help. Ask them to be your cheerleader, but also  help you find ways to be more outgoing. Visualize going through the steps and then practice different interactions with a person you trust. You can start with small interactions like saying hi to an acquaintance and then build from there by saying hi to a stranger. From there, you can talk about the weather, give a compliment or ask for the time. Use body language to show that you are open to more conversation and see how the interaction develops. In certain situations it may be necessary to find a professional. There are different kinds of people who can help you. Depending on how shy you are, you may need more than one kind of help.  Therapists can help you see patterns in your behavior. Cognitive therapy has been shown to measurably help with shyness.  Relationship counselors specialize in helping people express themselves in intimate relationships.

TL;DR in Vietnamese:
Lập chế độ khen thưởng. Tìm một người bạn để giúp đỡ. Nghĩ về những hoạt động bạn có thể làm để bắt đầu một cách thoải mái. Tìm chủ đề trò chuyện thích hợp.