One thing Heidegger got right is that we are future-oriented beings. We are aspirational. We have marvelous visions of what might be, and, as we grow older and realize that this is as good as it gets, we resist.
We can't quite accept it. I still half-expect to stumble into a more real, more acceptable world. Where grown-ups are in charge, and there is a bit of grace and restraint... But I know we all have slightly different visions and ideals, and I don't want to impose mine on anybody.
I remember imagining during the summer holidays at the age of sixteen that I would go back to school and we boys would shake each other's hands and behave in a sensible manly way. But, of course, it wasn't like that. It never is (or not for long, at any rate).
The ideal in my head is a muddle of clichés; overlapping ideals actually, incompatible, inconsistent, but each one bearing a family resemblance to the others.
This is more than ideology, but it is where ideologies come from. Political ideologies select and simplify and make consistent.
Activists, more often than not, become victims of their own activism one way or another, victims of a thin, distorting vision that can capture and even destroy vulnerable minds. Tempted by notoriety, they can come to see themselves as heroes, and are often egged on in this regard by sections of the media and other cynical players.*
On the other hand, in a world where traditional social groupings and functions are breaking down, joining others in a common cause can fill a need for meaning and purpose as well as purely social needs.
In the end, however, I think it's better to try to juggle the inconsistent whole and keep as many possibilities alive as possible for as long as possible.
* I have seen a number of such people come to grief, and I wrote a piece a couple of months ago on young anarchists. Aaron Schwartz was a different kind of radical, but he also seems to fit the pattern I have described.