Before you start, make sure you have the following information:

- ActiveCampaign API URL
- ActiveCampaign API Key
- MySQL database credentials (host, username, password, database name)

1. Log into your MySQL server.
2. Create a new database or select an existing database where you want to store the data.
3. Define the schema for the tables that will hold the ActiveCampaign data. Make sure the table structure corresponds to the data you will retrieve from ActiveCampaign.

Example:
```sql
CREATE TABLE contacts (
   id INT PRIMARY KEY,
   email VARCHAR(255),
   first_name VARCHAR(100),
   last_name VARCHAR(100),
   phone VARCHAR(50),
   -- Add other fields as needed
);
```

You can use a programming language like Python, PHP, or Node.js to write a script that will connect to the ActiveCampaign API and retrieve data.

Here's an example in Python using the `requests` library:

```python
import requests

api_url = 'https://youraccountname.api-us1.com/api/3/contacts'
api_key = 'your_api_key'

headers = {
   'Api-Token': api_key
}

response = requests.get(api_url, headers=headers)

if response.status_code == 200:
   contacts = response.json()['contacts']
   # Process the contacts
else:
   print('Failed to retrieve data:', response.status_code)
```

Extend the script to insert the data into MySQL. Continuing the Python example:

```python
import mysql.connector
from mysql.connector import Error

# Connect to MySQL
try:
   connection = mysql.connector.connect(
       host='your_host',
       database='your_database',
       user='your_username',
       password='your_password'
   )

   if connection.is_connected():
       cursor = connection.cursor()

       # Insert data into MySQL
       for contact in contacts:
           insert_query = """
           INSERT INTO contacts (id, email, first_name, last_name, phone)
           VALUES (%s, %s, %s, %s, %s)
           ON DUPLICATE KEY UPDATE
           email = VALUES(email),
           first_name = VALUES(first_name),
           last_name = VALUES(last_name),
           phone = VALUES(phone);
           """
           cursor.execute(insert_query, (
               contact['id'],
               contact['email'],
               contact['firstName'],
               contact['lastName'],
               contact.get('phone', '')
           ))

       connection.commit()

except Error as e:
   print("Error while connecting to MySQL", e)

finally:
   if connection.is_connected():
       cursor.close()
       connection.close()
```

ActiveCampaign API may paginate the results if there are a lot of contacts. You'll need to handle this in your script by checking for a 'next' link in the API response and making additional requests as needed.

To keep your MySQL database up to date, you'll want to run this script at regular intervals. You can use a cron job (on Unix-like systems) or Task Scheduler (on Windows) to schedule the script.

Add error handling to your script to manage API rate limits, timeouts, or unexpected responses. Logging is also important for monitoring the script's performance and troubleshooting issues.

- Ensure your API key and MySQL credentials are securely stored (e.g., environment variables, secure app config).
- Use HTTPS for API requests to protect data in transit.
- Sanitize data before inserting it into MySQL to prevent SQL injection attacks.

Test your script thoroughly to make sure it handles all edge cases, errors, and reconnections after failures.

Regularly check your script and database to ensure that the data transfer is working as expected. Update your script as needed if ActiveCampaign changes their API.

By following these steps, you should be able to move data from ActiveCampaign to MySQL without using third-party connectors or integrations. Remember to comply with all relevant data protection regulations when handling personal data.