I’m just a fellow Mandarin student myself, but here’s how I see it: Chinese does not have verb tense — it only has verb aspect. 今天不想再去了 means “I'm not planning on going again later today.” The 了 just means that the action is thought of as complete — in this context, as being (actually not being) completed in the future. It’s a bit like the future perfect in English: “Will have gone”. Actually, there is a closer parallel in the Slavic languages, but I’m afraid I wouldn’t know about Hindi.

Edit: I originally forgot about the 不 when posting. This does not change the analysis, however.

Edit 2: It occurs to me the 了 may actually apply to 不想, in which case the meaning would be something like “I don’t plan on going anymore” / "I no longer want to go" (as in, “I have abandoned my plan to go”).