You did the right thing on the first joint when you held the joints together for a few seconds. There's almost certainly enough pipe in the other fittings to hold. FYI: The so called PVC glue or cement is neither glue nor cement. It is a solvent that briefly liquifies the surfaces of the pipe and fitting. When the pieces are joined the two surfaces mix together and form a chemical weld. Not unlike a metal weld. It's good practice to give the pipe a 1/4 or so twist when inserting it into the fitting, but that's not always possible nor is it really vital.