I could see Brutus/Cassius in the days before Philippi, once Brutus has realized that he's made a Terrible Mistake, and decides that having made this bed of treachery he now must lie in it. It is like a weird mixture of self-punishment and comfort in the last days before a battle that he knows will be disastrous.

I found Tobias Menzies disappointing at Brutus, precisely because he did seem like a good match for Cassius. Not nearly noble and self-sacrificing enough!