We can choose to take certain actions based on our personal motivations, but there is always a principle of striving forward in the first place. This striving, according to him, leads to inevitable suffering... We are always in a state of "lack" in which we are trying to remove said feeling, but in vain. — schopenhauer1

…you just made me think of how Schopenhauer's view of character being inborn can be related to Sartre's authenticity. Perhaps Sartre's radical freedom, or being authentic, is actually just the playing out of what one's character actually wants. It is finding the motivations which actually suit one's character. — schopenhauer1

I’ve found that when I don’t try to will beyond my capabilities, or be something that goes against my natural character (as it’s evolved to be), there is actually less sense of striving. I’m still acting to fulfill my desires, but there is more acceptance of whatever results I get, and less tension. Action has more a sense of exploration, of adventure, and less of “I need to accomplish this”.

For me, a clear example is in a martial art sparring practice I do. It’s a game of trying to push your opponent off balance, while preventing your opponent from doing the same to you. When I’ve approached this with the idea of “winning”, I tense up more and push harder, and get frustrated when I can’t manage to move my opponent. The game becomes like wrestling, and I have a feeling of needing to win in order to feel accomplished.

When I’ve instead approached this game with more of an attitude of exploration – of finding out what I can do, and enjoying the interchanges that go on – I’m more at ease. I’m still playing the game, but I’m not over-exerting in order to win (interestingly, I also perform better during these times). I’m playing in a way that’s being honest to my actual capabilities.

I’m now thinking that both Schopenhauer’s, and Sartre’s, views are needed to give a full picture of the human condition. That is, taking either side without regard for the other ends up lacking.
I’ll use my current situation in life as an example. Software engineering is my profession, and I like philosophy, but don’t spend nearly as much time on it as my full time job. If someone said “define yourself”, “software engineer” seems a more appropriate answer than “philosopher”. Now I could choose to answer “philosopher” anyhow, but that would be contrary to the reality of my situation, which is as it is regardless of how I “define myself”. Actually it would cause dissonance in my mental states, as I’d have to try to ignore the fact that much more of my time is spent engineering software.

From the above, Sartre’s view seems absurd, and Schopenhauer’s seems right on – there is an actual reality to my life, which makes me as I am; any self-definitions I come up with are superfluous.

I could however take action, and quit my job and go back to school to get a degree in philosophy, and do this full time. I can’t whimsically define myself however I want, but I can start with some idea in mind, and take steps to bring that about (which involves time, resources, and constraints). I can will myself to be a philosopher, within limitations. But the fact that I choose to will this would already be based on pre-conditions of myself – a desire to do philosophy, and that desire itself isn’t something I chose to have. So Sartre’s view still looks totally wrong.

I could also ask: is it desirable to have a desire to do philosophy? Suppose I deliberated and found the answer is “no”. Given real constraints, I may not be able to change this desire, but through this I’d realize my desire must be grounded in something (some complex interaction between my makeup and the world) as opposed to being “just there”. My desire isn’t essential to “me”, but rather is held in place by my life’s situation – which given the right conditions, could change such that I no longer desire to do philosophy.

There is a sense of non-definitiveness, of freedom, in considering that everything about “me” is conditioned and in principle changeable (even if, given time and resources, it couldn’t actually change in my lifetime). So this is where an “extreme freedom” view makes sense – but it necessarily includes the aspect of life as conditioned and constrained by the world as it happens to be.