What is the best time to enter? Is there a strategy for entering that you can explain, please?

What happens to you is often called a common psychological and behavioral effect among traders, and its causes can be:

Late entry ⏰: Many people enter after the currency has risen significantly (FOMO - fear of missing out), so it’s normal to see a price correction after their entry.
Rapid volatility 📉📈: Cryptocurrencies are highly volatile, so any small movement after buying may seem like a "big drop" even if it is just a normal correction.