Getting close to one's backyard birds is not always so easy. I'm fortunate in that I have plantation shutters on the picture window that faces my backyard birdfeeders, and I can keep the blinds partially shut to block the birds' view of me. In this way, I can often get within inches of visiting pine siskins, American goldfinches, house finches, California quail, and other guests without them wising up to my presence.
There are ways to get close to birds without blinds, however. Birders who provide a generous food or water source will find that birds grow more bold as they become more comfortable with the surroundings, and if they feel safe they will often disregard your presence even if you aren't that far away. Window feeders can also bring the birds up close, though I'd recommend a design with a back mirror to keep the birds from noticing your observation. Of course, good binoculars or a spotting scope can make you seem as if the birds are mere inches away, regardless of how physically close you are.
Getting close to the birds truly brings this hobby alive and makes it all the more fascinating. I'm often close to pond birds (we feed ducks and geese regularly), I have my faithful -- and famished -- backyard guests, I was privileged to be less than twenty feet from a wild golden eagle, and I've fed western scrub jays from my fingers. As I draw closer to each new bird, they become closer to my heart, and that connection is a birder's greatest privilege.