I applied for a Spanish visa, but it was rejected. I don't know why.

Spain is a developed country, and it is normal for applicants to refuse visas, because the embassy is very strict with applicants, but you don't need to worry. It is not terrible to be refused a visa. After refusing the visa, you need to analyze the reasons for your refusal. Generally speaking, visa refusal is a matter of materials. /zd/ym