By this verse.. some have the SPirit of Christ(God) and some DO NOT.. WHich implys not all christians are christians.. or that being a christian is not a matter of what you say you are.. You might not be... Jesus said.... "You MUST be born again".. the first birth is not good enough..
About going to "church"... You can put puppies in a muffin tin and put them in an oven(church) but that don't make them muffins after processing..... Puppies are puppies and muffins are muffins..