Divide and ConquerDivide and 'zone' the space with shelves (like ) and credenzas. If you stick with light colors and keep the shelves organized you can cordon off some private space and keep your office from invading your bed.
Think Scale: the same giant living room furniture might not fit into a studio, you may need to downsize to a loveseat and a footstool instead of a coffeetable, or 2 armchairs and a side table instead of a sofa.
Focus: Try arranging around a focal point, either putting your bed front and center or with shelving that covers one wall with all the furniture oriented around that. If you're lucky enough to have a fireplace use that as a focal point, do not use your heater as one.