Judging by the out dated decor, disgusting table tops, plastic chairs and 50 year old floor mats I can assure you the kitchen needs upgrading and has probably never been professionally cleaned.
I dropped in for Christmas Eve and I couldn't believe how rude the staff was. I politely asked if I could please make a basic substitution on one of their diner specials and I was told by the lady taking our order they usually charge 2$ for the request, but since they were so busy due to Christmas Eve they couldn't accommodate it and I would have to order the dish separately. She's one of the main servers / managers there, and every time Ive seen her she has been miserable. The tone of voice and body language were shockingly rude, and needless to say I told her I'd go elsewhere.
Personally I prefer supporting happy, friendly, and respectful business owners. Even the main manager at the door and that takes orders by phone/walk-ins is miserable. Lighten up and perhaps treating your customers with a smile will come easier, since clearly you have no passion for your business.