Great tips so far. Regarding your photo of a stuffed pannier with "almost all" your clothing--looks like too much clothing. One way to look at it is that you should be able to wear everything at once as part of a coordinated layering system. That way, everything should fit easily into less than half a pack for three-season touring. This is where Machka's comment about multiple uses is very good. For instance, on tour I wear a long sleeve nylon trekking shirt with a collar and pockets--good for sun and bug protection, carrying valuables safely, sleeves can be rolled up and down and buttons undone for ventilation, washes easily and dries quickly, layers over a polypro jersey and under a rain jacket for a wide range of temps, and even looks decent enough (when clean) for town wear and travel.
Ditto the comments on amount of food and water needed. As experience and fitness increase, you may find you need to carry less, if any.
And you'll start to actually enjoy the hills, because you always come down them. I once heard a comment that rookies complain about hills, experienced cyclists complain about wind.