I started out like that now I lock most of my junk in my desk. I still carry clothes changes but the shower kit and towel and all that fun stuff stays at work. Two panniers and I am good.

I take my cats to the vet in a soft-sided pet-carrier that can be worn like a backpack.

The cats don't like it much, but it's only a 10-minute ride, and they complain just as much if we go in a taxi.

I too tend to carry as much stuff as I have room for, so I have to restrict myself in pannier size I have a set of smallish panniers and recently moved down to a much smaller handlebar bag.

In handlebar bag: wallet, snack, first aid kit, cell phone, keys, Swiss Army knife, mini pump
In R pannier: work clothes & shoes
In L pannier: spare tube, patch kit, tire levers, multi-tool and 13mm wrench (old Raleigh, takes a weird size); jacket; U-lock if I am going to be stopping anywhere; lunch.

I've taken mine in a trailer...

riding with a backpack is awful... does anyone else feel the same way? i haven't resorted to panniers yet, maybe a trunk bag will suffice but i have yet to try. has anyone else made the switch from backpack to pannier? convince me the grass is greener on the other side!

I wore my backpack with a change of clothes and lunch my first day commuting and it was okay, but eh. The next day, I figured out how to mount my rack (it was weird with a step-through). and got a pair of Novarra grocery-getter style panniers. My next ride to work, I stuffed that same backpack in there plus had room for an extra bottle of water.

I felt 100x better without it on my back.

Go for it.

My '83, lugged-steel road bike weighs in at over thirty pounds.
If I carried more than what I needed, I'd have to factor in "stop-and-vomit" time.