The game is VERY INVOLVING. You will be fighting, but you must keep building more guys, upgrade, think about what he might do after the battle, scout for expansions, expand yourself, save your hero, focus fire... It can be overwhelming.
So play with a clear mind so you won't get frustrated. That's probably the best advice there is.
One last note is always do something. What I mean is I see players watch their heroes heal or sit with their armies just because they lost a battle... Always move and keep the initiative. Make sure he responds, rather than waiting for him to come to you.
And if you have an army with the power of 2 and he has the power of 3, don't fight his army. Instead, go to his bases and do as much damage withOUT confronting his army. It really helps.