In general I think you should always review at least for those conferences/journals that you publish in yourself too. So, I simply consider it my duty and obligation to the field.

That said, I learn a lot from reviewing which also makes me want to voluntarily do it again. Different perspectives, different approaches, sometimes a peak into interesting new research directions, writing styles. There's a lot to learn from other people's work. Also, since I tend to read mostly literature related to my field, sometimes reviewing a paper that is outside my own narrow scope can be quite refreshing.

Sadly, I have the feeling that new reviewers are not always properly instructed / taught how to review by their mentors/superiors. This can lead to poor quality reviews (short, uninformative, using bad language, etc).

I'd very much advise you to always keep in mind: 'the person at the other side of this paper is just like me, struggling just like me, putting in insane amounts of effort just like me, and hoping to make a small impact just like me'.