Questioning the 'aim high' ideal

I've been engaging in a round of goal setting and whatnot as part of self.fix() lately. Looking at the advice out there, it seems that a common wisdom is to set barely-achieveable goals, on the theory that if you fall short, hey, you improved, awesome. The idea is, the higher your goal (so long as it's within the realms of potentially realistic) the more you'll achieve in a given period of time.

This is not how I work.

I've tried that approach in the past, and what's happened is the first time I slip up I get a little bit depressed (because I know how slim the margin of success is) and it gets worse as time goes on. Not to mention that the further I'm going to undershoot, the more anxious (and depressed) I get about the whole thing as time goes on. Or, I go all out - and break myself in various ways.

This time, I'm trying a new approach: lots of small goals. Part of this is my Achievements posts; they're recording the tiny, mediocre, mundane goals I achieve on a day to day basis. A way of reminding myself that I am accomplishing something.

Likewise my fitness goals. My workout yesterday set a baseline from which to improve. Whilst I do have very long term goals, these bear little to no resemblance to my shorter term goals. 

So I have goals like eating twice a day, cooking four dinners a week. Improvements on my current situation, and a bit of a stretch for me right now, but certainly not earthshaking or awe-inducing.

I was asked yesterday by one of the guys at the gym what I'd aim to get out of a 12 week lose and shape up course. When I told him that I would aim to increment my exercises such that I would see an improvement over the course of a month, he ran off the spiel about aiming high. When I told him that I'd tried that, and it was for me a recipe for depression and failure, he was surprised, but became less so when I explained the burnout and the anxiety/guilt mechanisms behind it.

I know that with mediocre goals there is, for most people, a temptation to coast and rest on their laurels. Not so for me; until I get to my endpoints, every time I achieve a goal, there will immediately be another replacing it. When I get to the point where I can easily do 10 knee pushups, for instance, I'll start alternating with full pushups until I can do 10 full pushups easily. As I achieve each goal, I'll plan an extra increment beyond the new goal.

For me, continual adaptability is the key; life throws me curveballs, and in order for those to not completely throw me off, I need to have a maximally flexible approach. At the same time, I desperately need structure and plans to follow, otherwise I'll sit on my backside and do nothing at all.

The constantly incrementing mediocre goalset seems, to me, to be a way to satisfy these seemingly mutually exclusive needs.

What are your thoughts on goals, planning, goal setting, and how they interact with success and failure?