Begin by logging into your Drift account. Depending on the data you're looking to export (such as chat transcripts, contact lists, etc.), navigate to the relevant section. Use Drift’s built-in export feature, typically available in settings or the data management section, to download the data. Export the data in a CSV or JSON format, as these are commonly supported and easy to process.

Once you have the exported data file, open it in a text editor or spreadsheet application. Ensure that the data is clean and well-structured. This includes checking for missing values, ensuring consistent data types, and correcting any formatting issues. If the data is in JSON format, you might need to convert it to CSV for easier handling, using a script or an online converter.

Ensure you have PostgreSQL installed on your system. If not, download and install it from the official PostgreSQL website. Along with the server, install client tools such as `psql`, which will be used to interact with your PostgreSQL database.

Open your terminal or command prompt and access the PostgreSQL command-line tool `psql`. Connect to your PostgreSQL server using the appropriate credentials. Create a new database using the command:
```
CREATE DATABASE drift_data;
```
Switch to the new database and create tables that match the structure of your data. For example:
```
CREATE TABLE contacts (
id SERIAL PRIMARY KEY,
name VARCHAR(255),
email VARCHAR(255),
created_at TIMESTAMP
);
```
Adjust the table schema as necessary to fit the columns and data types of your exported data.

Use the `COPY` command in PostgreSQL to import the data from your CSV file into the database. First, ensure the CSV file is accessible by the PostgreSQL server. Then, execute the following command in `psql`:
```
COPY contacts(name, email, created_at)
FROM '/path/to/your/data.csv'
DELIMITER ','
CSV HEADER;
```
Replace `/path/to/your/data.csv` with the actual path to your CSV file. Ensure that the column names in the `COPY` command match those in your table schema.

After importing the data, verify that the data has been correctly loaded into the PostgreSQL database. Run a few `SELECT` queries to check the data:
```
SELECT FROM contacts LIMIT 10;
```
This will display the first ten entries in your table, allowing you to confirm that the data is accurate and complete.

If you need to perform this data transfer regularly, consider writing a script to automate the process. You could use a shell script or a Python script using libraries such as `psycopg2` to handle the database connection and data insertion. Schedule this script to run at regular intervals using cron jobs (on Unix-based systems) or Task Scheduler (on Windows).

By following these steps, you can successfully transfer data from Drift to a PostgreSQL database without relying on third-party connectors or integrations.