Begin by logging into your Insightly account. Navigate to the data section you wish to export (e.g., Contacts, Leads, Projects, etc.). Use the built-in export function, typically found under the 'Actions' or 'More' dropdown menu, to export the data in a CSV format. This file will serve as the raw data you’ll import into PostgreSQL.

Open the exported CSV file using a spreadsheet program like Microsoft Excel or Google Sheets. Review the data for any inconsistencies or errors that may need correction. Ensure that all fields are correctly formatted and consider renaming columns to match the naming conventions you plan to use in PostgreSQL.

Access your PostgreSQL server using a command-line interface or a GUI tool like pgAdmin. Create a database to hold your data using the command:
```sql
CREATE DATABASE insightly_data;
```
Switch to the newly created database and create a table that matches the structure of your CSV file using the `CREATE TABLE` statement. Define the column names and data types to correspond with those in your CSV.

Ensure you have PostgreSQL client tools installed on your machine. These tools include `psql`, which is the command-line utility for interacting with PostgreSQL. On most systems, these tools can be installed through your package manager or downloaded from the PostgreSQL website.

Use the `COPY` command in PostgreSQL to import data directly from the CSV file into the table you created. This can be done via `psql` with the following command:
```sql
\COPY your_table_name FROM '/path/to/your/file.csv' WITH (FORMAT csv, HEADER true);
```
Replace `/path/to/your/file.csv` with the actual path to your CSV file. The `HEADER true` option indicates that the first row of the CSV contains column headers.

After loading the data, perform a series of checks to verify the integrity and accuracy of the imported data. Use SQL queries to count rows, check for null values, and ensure that data types are consistent with your expectations. For example, you can run:
```sql
SELECT COUNT(*) FROM your_table_name;
```
This will confirm that the number of rows matches those in your CSV file.

If regular data updates are required, consider writing a script using a programming language like Python or Bash to automate the export from Insightly and import into PostgreSQL. Use cron jobs or task schedulers to run the script at regular intervals. This step is optional but can greatly enhance efficiency if frequent data transfers are necessary.

By following these steps, you can successfully move data from Insightly to PostgreSQL without relying on third-party connectors or integrations.