suppose what I could be

假如我
doing instead of watching a half an hour of television

不是看半小时电视
is being at a really great party.

而是参加了一个很棒的派对
Then we might say,

那我们可以说
the fact that I'm stuck home watching television

我窝在家里看电视
is bad for me in this comparative sense.

相比之下对我是坏事
It's not that it's, in itself,

并不是说看电视本身
an unpleasant way to spend some time;

是一种不愉快的消磨时间的方式
it's just that there's a better way to spend time that I could be doing,

只是我还可能有更好的方式来消磨时间
in principle at least.

至少原则上是这样
If only I'd gone.

如果我去了
If only I'd been invited.

如果我被邀请了