The first scene was shot using mainly light sources within the scene, the computer screen to light the face when sitting at the computer, a small amount of natural light creeping through the window to act as a small amount of fill light and lighting the room. I also used an extra fill light by the bed to light this area when the actor was reading the paper. I went for a slightly unsaturated look, to emphasise the feeling of depression, and the large areas of darkness throughout the scene I hope also portrayed this.
The second scene was shot on an overcast day, and I used a trick I had learnt to make it appear like evening (underexpose the image by a couple of stops, and set the white balance to tungsten, then desaturate and correct the colour a bit in post production). This not only created the look of evening, but also created a frame with a lot of dark, masking a lot of the detail, creating a bit of tension and mystery about the frame.
If I had more lights to use, I would have lit the first scene much more, and had more control over the lighting. I had to work at a fairly high ISO as I had cut most of the light out of the room, in order to control it better, but if I had more lights I would have added more fill light to the room to balance out the light and dark a bit better, and remove some of the shadows on the back wall. I would certainly keep the strong contrast between the light and the dark side of the actors face though.
The second scene I'm not sure I would have shot much differently. I might have shot it at night with some lights to light the scene a bit, but I am satisfied with the look I achieved. Overall as well I would have used some gels on my lights to balance the temperature better, as I couldn't use tungsten lights in with the lights in the first scene as the colour temperatures were different.
Lighting is key to a production. Good lighting often sets apart a big budget production from an amateur production. Control of lighting certainly helps create a mood to a scene, and can give a sense of a location or a time of day or something similar.