i would give myself the ability to delay gratification. i have a problem balancing what's best for my long-term self and what's good in the here-and-now. Partly because tomorrow isn't promised, but mostly because i can't tell myself "no." That's why i drink too much and eat shitty food. It's short term satisfaction over long term fulfillment.
i would also allow myself the freedom to be myself. [mostly] all of us put up some sort of a facade. some just a little, and others full-on performances. i'm mostly real, but i still don't feel like i'm able to be fully transparent.
i would find the motivation to jump out of bed early each morning and fill my days with worthwhile accomplishments. I don't know why i'm unable to do this now, but the lure of the warm comfy bed in the morning is undeniable.
I would eat more cleanly. My diet would closely resemble the Paleo Diet, even though i wouldn't subscribe to any particular school of thought.
I would also inject more leisure into my life. Downtime is currently spent in a boring manner, laying about. It's largely about the energy the energy levels, which can be improved greatly by a clean diet, exercise, and plenty of sleep.
i'd give more of myself to others. i am somewhat selfish. i can go to much greater lengths to make sure the beings around me are comfortable. Taking my dog on more walks and trips to the park, for example. He loves his life -- it's not like he's neglected, but i could make sure he had more fun.
I'm sure there's plenty of other things that i could change but that's a decent list to get me started. All of these have the ability to be improved upon.