I'm proud of you. But if your child works especially hard on a challenging assignment and completes it successfully, that's worth celebrating. Praise generously, yet honestly. Praise will lose its effectiveness if used indiscriminately, plus a child can usually tell when you're not being sincere. Direct praise to the task at hand.
Specific praise guides future behavior.
Starting every homework session with the Star Wars theme might be going overboard. And you don't have to be deadly serious about it. Laughter, shared jokes, and even a tickle or two can go a long way toward lightening the homework load. Use timers and competition wisely. If the latter seems true for your child, put the timer away.