Striking that delicate balance in life

Do we usually stop thinking at a particular time in life? After all, life becomes a constant, and the usual hum-drum of go to work, work work work, and go home to work, seems to continue day after day.

Yet, how can life be so? It's so...unnatural, so boring, so not worth living. I have a habit of planning milestones in my life - things I wish to accomplish: big things to me. It seems unnecessary and extra to people I speak to, but these are achievements that can make me feel that the learning curve has not reached a plateau, and more importantly, that I haven't stopped thinking.

But one wonders...when work piles up, and time is limited, how much affordances of strength and vitality does one have to keep this going?

There is a need to know how much to stretch one's self, without over-stretching. While a life without milestones is probably not worth living, this fruitfulness of life needs to be balanced out for personal sanity.