Nothing can be more pestering than a 3D-Print letting go of the print bed in mid print. Your 3D-Print will then move and your whole print is ruined. If this happens the adhesion of your 3D-Print to your print bed was insufficient and needs to be improved.
A proper adhesion between the print bed and the 3D-Print is easily accomplished with Kapton spray. This is a unique adhesive spray that is applied to your heated bed and when its heated it turns into a sticky material that will hold the 3D-Print properly in place. This will prevent the 3D-Print from letting go of the heated bed and also will prevent the bottom of the print from warping.
Make sure to let the heated bed cool down to room temperature before trying to remove the 3D-Print. The adhesive loses its strength when it has cooled down again. Prematurely removing the 3D-Print will most likely end up damaging your print or worse, your heated bed.