When you're in a production there are things you can do something about, and things you can't. The script may not be any good. The production may not be any good. The other performers may not be any good. You may not be any good. You may be struggling with your performance. There isn't much you can do about those things in the course of one rehearsal period. But there are things you can do:
Learn your lines
Learn your cues
Learn other people's lines
Study the story
Understand the motivation for everything you do - write it down
Learn those motivations
Practise your physical challenges - sword fighting, dancing, puppetry, loading a gun
Look into the other versions of the story
Read around the part
Learn the staging
Meet someone who has the experience of the character you are playing
Become an expert on what you're doing
When everything's going well these things look after themselves, but when things aren't going well, if no-one is helping you, give yourself the best chance by doing these things. If it doesn't help it will be rewarding anyway - it's a chance to learn some things. Presumably you are interested in drama and plays/ operas/ scripts/ staging or you wouldn't be doing this.
Plus, don't judge the show until it has an audience - you just never know!