It's two particles; happens to be followed by .
* is a plain object marker, but apparently it marks an object in the _previous_ sentence. Is there a transitive verb without a corresponding object in the previous sentence, for example , , , etc? The word order is reversed and the sentence is split into two for emphasis. Saying the verb first is a common rhetoric device in Japanese (known as /hyperbaton). Typical example is:
> Change the world!
* is a sentence-end particle for mild emphasis. It's like "you know" or "yeah" but you can ignore it in translation. The verb is irrelevant.
* * *
**EDIT** : Now that OP posted the previous context, I can say is the direct object of after . "It's far more worthwhile to do it alone. (I mean,) Doing the practice of 3!"