Playing the Score
The same trick means something different depending on the score: comfortably ahead you play it safe, badly behind you take risks you'd never touch otherwise. Of the 120 Augen in play the declarer needs 61, while the defenders only need 60. Where the round currently stands changes what the right card even is.
Read the official scoring rules.
Ace and Ten of Hearts: twenty-one Augen sitting in two cards. Whether you chase them or let them go depends entirely on the score.
Already won? Play it safe
Keep counting as the round runs, so you know the moment the line is crossed: 61 Augen as declarer, 60 as a defender. Once your side has reached it, the round is yours no matter what happens next, so stop taking risks. Say you're on 64 Augen and still hold the Ace of Clubs and the Seven of Diamonds. Play the Seven and let the trick go: the Ace only adds a few more Augen and can still be ruffed away. Only while Schneider is within reach is it worth collecting more.
Behind? Take the trick
Badly behind late in the round, the calculus flips: a trump you'd normally save is worth spending right now if it's the only way to win the trick. Say three tricks are left, you and your partner are on 40 Augen and need 60. The Ace of Spades and the Ten of Spades are on the table, twenty-one Augen, and you're out of that suit. Then ruff in with the Jack of Hearts, even though you'd rather have kept it for the last trick: the Jack brings its own two Augen along, that puts you on 63, and a later trick that may never come won't help you then.
Can't win this one
Not every trick is yours to take. When nothing in your hand beats what's already on the table, don't waste a good card trying. Say the declarer led the Ace of Spades, your only Spades left are the Ten and the Eight, and you have no trump. The Ten can't beat the Ace; it would only hand the declarer ten Augen. Follow suit with the Eight of Spades and save the Ten for a trick you can actually win.