Apparently the particle "le" can only be used with actions that can be completed. WRONG! It is just plain wrong to say that, so unlearn it. 了= completion, in the broadest sense possible. It's going to take you many months before you fully comprehend this particle. I recommend you take it step by step, rather than trying to understand everything immediately. Love and like are states, and these states can change, and when the change has been completed you use the particle 了. Wo bu ai ni le （我不愛你了） = I don't love you any more. P.S. Don't fool yourself into believing you can learn Chinese without studying the characters. It's alright at the beginning, but blah blah blah.

I want to notice you, many chinese characters are some tones,however you write pinyin with the number-tones,we also hard to understand it meaning.I suggest you express it in english more clearly or give our some samples.

Thank you, everyone! Unfortunately, I don't have a Chinese grammar book, and since I will be travelling for the next few months, I cannot have one (no fixed address to send it to!). I'm learning from Internet and, as you can see, there is a lot of superficial or wrong information about Chinese grammar. I'd love to learn characters, but have no time now. Would it be easier for Chinese readers if I write the pinyin with the number-tones? Thanks again for your help!

I don't love him anymore. 我不再爱他了。 I loved him, but now I' don't. 我爱过他，但现在不爱了。 I thought he was nice, but I found out he was cheating on me. 我曾经（原本）以为他很好，但我发现他是在骗我。

Apparently the particle "le" can only be used with actions that can be completed. WRONG! It is just plain wrong to say that, so unlearn it. I agree with Eilot. Normally it means an action is complete, but not always. e.g. 我要睡了。(wo3 yao4 shui4 le) I am going to sleep. 我要吃了。(wo3 yao4 chi1 le) I am going to have something. 要和了一起用是特殊情况，记住就可以了. Just remember this case with yao4 and le as a special case. At last, I need to point out that: “了” 放在句末轻读，没有声调 （le）。