Man, when I started I was tanked when I got home too but my ride is nearly flat. Now I barely notice the ride by the time I get home, unless I am grinding in a nasty headwind, and actually workout for an hour or so once I get home. Keep at it and take it easy. If you have a computer on your bike turn it so you can't see it. There is no point in looking at the speed when grinding like that. Just know that every pedal stroke is one less pedal stroke to the end of the climb. It is not a race it is a commute, I have a hard time remembering that all the time. If you have time, watch a pro cycling race and see how fast they roll on flats then once they hit the mountains they grind to a halt. Some even get dropped so bad they have to quit the race.

In short, keep at it. You'll get there!