Touching your sore with unwashed hands can lead to a bacterial infection, and you could also spread the sores to another area of your body. Use warm, soapy water to wash your hands often throughout the day. When you have a cold sore outbreak, you are highly contagious and the virus can be easily spread to another person. Avoid kissing or having your cold sore come in contact with someone else. Similarly, avoid oral sexual activity during an outbreak. This can risk transmitting the virus and infecting the other person with genital herpes. Do not share drinking glasses, straws, toothbrushes, razors, towels, or other items that have come in contact with someone with cold sores. Similarly, do not share these items with someone else if you have cold sores. Throw away your toothbrush when you have a cold sore outbreak. You can risk continuing the virus if you keep exposing yourself to it through your toothbrush.

TL;DR in Indonesian:
Cuci tangan sering-sering. Hindari sentuhan antarkulit. Jangan saling meminjam benda-benda tertentu.