We've all done it - faced with attacking a heavy backspin, often deep on the table, you get nervous and try to weakly topspin it up, and it goes right into the net, plop. Often players get frustrated by this heavy backspin, saying or thinking, "It's too heavy! I can't lift it!" That, of course, is downright silly. Even spinning, the ball still weights 2.7 grams (less than a tenth of an ounce), and anyone who wants to can smack it up over the net and off the end. (I tested this theory once with a two-year-old, who sat on the table and had no trouble smacking my heaviest multiball backspins toward the ceiling.)
The real problem is that your instincts tell you that if you aim up, you'll go off the end, and so while you know you have to lift, your subconscious doesn't want to do this. That struggle results in those weakly hit shots into the net. (Or, for some, wild shots into the net. And for others, an over-reaction where they throw their training to the wind and try to consciously guide the shot and end up lifting it off the end.)
How do you overcome this? As usual, it involves practice. Find someone who can push heavy, or feed multiball with heavy backspin, and simply get used to it. You have to make it a habit, because only then will your subconscious learn how to do this. And then it'll be automatic.
The catch is that if you've spent years struggling against heavy backspin, having trouble with it has become ingrained. Overcoming this will take two things: 1) Practice; and 2) Willingness to miss a shot in practice. Why the latter? Because it is that ingrained wish to make the shot that causes your subconscious to fight against the actual need to lift against the heavy backspin. Once you decide that all you want to do is topspin the ball up over the net, even if it goes off the end, then your conscious and subconscious minds can work together and ingrain just how much you should actually lift against a heavy backspin.
And now for the key part, right from the title. If you struggle lifting heavy backspin, have a simple rule - Never topspin into the net. Don't worry about going off the end, all you want to do is arc that ball over the net, and not worry about the rest. If you do this, then your technique, timing, and ball control for the shot will develop, and the topspin in the ball will pull it down and give you consistency.
And then repeat to yourself, over and over, "Though I loop against the heaviest of chops, I will fear no backspin." Amen!!!