I get this error when i leave my PC for hours after i drag and drop data from SDE connection
That's a low-level database error, not anything Esri could have control over. A database server reboot or over-enthusiastic router configuration could generate this error, but there really is no way for us to know the cause.
As Vince noted- "Communication Link Failure" notifications often indicate a break in communication between the client application and the underlying database (SQL) server which can be caused by a wide range of culprits. See below for more information and troubleshooting tips.
C:\Program Files\Microsoft SQL Server\MSSQL##.MSSQLSERVER\MSSQL\Log
Retrieving data ...