Why go for holy causes when you can't fix your own life

If you're an egoist, the answer is "don't". For altruists, the answer is shut up and multiply.

You can get many more utilons if you buy them where (and while) they're cheap. If you are unhappy now, this may be very hard to change. You can probably get better mileage - in terms of expected utilons per unit of effort - if you concentrate on promoting developments that will permanently improve the human condition.

Failing that, assuming your own life is not severly messed up, you can likely still do better than by improving it further by finding people significantly less well-off than you are, and helping them. Research suggests that this is typically not as simple as giving them money, but even so it should be possible to make such help scale significantly better than attempts to significantly improve your own subjective well-being.

maybe it's a compensation mechanism, as Eric Hoffer suggested?

I don't care what you label it. I'm a bounded rationalist, and more so a bounded altruist - akrasia is a major issue for me. I will take all help from any of my mental modules to act in a more rational and altruistic manner I can get.