In Magic, knowing when to attack is a fundamental question. Naturally you attack when it helps you win. In limited games in particular, there are times when you and your opponent just go back and forth attacking each other, this is known as racing. You should race if you will win, which unfortunately requires a little math, but not much.
Your Turn 15 life, 2/2 creature – Opponent 7 life, 3/3 creature – Should you race?
The easiest way to figure out to race is to first calculate how many turns it will take for you to kill your opponent. Now compute how many turns it takes your opponent to kill you. Obviously if you can kill your opponent first, attack. In this example, you will win in 4 turns, and you opponent will win in 5 turns, so you should attack.
Your Turn 2 life, 3/3 creature – Opponent 5 life, 1/1 creature – Should you race?
Your Turn 5 life, 2/2 creature – Opponent 11 life, 1/1 creature – Should you race?
Your Turn 17 life, 3/3 creature – Opponent 15 life, 2/2 creature – Should you race?
Your Turn 19 life, flying 1/1 creature – Opponent 9 life, 2/2 creature – Should you race?
Your Turn 8 life, flying 2/2 creature – Opponent 7 life, 3/3 creature – Should you race?
Obviously you don’t know what cards your opponent will draw, but you can race to reduce his chances of winning. Racing increases your chances of winning because it puts pressure on your opponent. If you are loosing the race, you will want to trade creatures in combat, both of them will die, in hopes that you can draw a solution. In most games you will be both the aggressor, who wants to race, and the defender. Aggro decks are built upon the concept of racing, and hope to attack on every turn.
MTG Forge probably works best as a limited simulator and limited decks tend to attack alot compared to some types constructed decks. Limited control decks do exist, but usually they win by brutally attacking.