Clearing vars and tabs....
That sounds as though you are programming with all of your variables as Global variables. If that is the case I would suggest changing your programming practice to make use of local variables which are cleared each time the procedure or method is called.
If you have to use global variables because ABAP requires them, do not access them directly but pass them as parameters to your procedures or methods. If you have data that is reused then consider making the table static.
In other words don't use global variables unless ABAP forces you too as they cause more problems than they help.