Caffeine increases alertness and brain activity, but individuals have major differences in tolerance levels. Generally, starting your morning with 75–100mg of caffeine (about one mug of coffee) is a good starting point. Drink less (or none) if you experience unpleasant jittery sensations, muscle tremors, or a major crash after the caffeine wears out. Drink more if you don't notice an effect.  Caffeine helps you function faster and push through relatively easy tasks. It won't make difficult tasks easier or help you find solutions to complex problems.  Teenagers and young adults should stick to 100mg of caffeine a day, while most adults can handle up to 400mg spaced throughout the day. Note that these are recommended maximum limits, and that a lower dose may have better effects on your mood and energy level. Most people who regularly drink coffee or tea feel an oncoming mood boost within minutes of starting their beverage. The full energy boost, however, usually takes 45–60 minutes to reach its maximum, then peters out over the next 3–6 hours. This varies a great deal between individuals, but it's a good estimate to keep in mind. If you don't drink coffee until you show up to work, you may still be groggy for that morning meeting. In theory, a small hourly dose (e.g. 20mg or 1/5 a mug of coffee) may give a more steady boost and less extreme crash. One study suggests this increase brain function but not a feeling of alertness, at least in sleep-deprived people. Many other substances affect how your body processes caffeine. Know what these are so you can maximize the energy you receive, or reduce it to a more mellow buzz:  Sugar might increase the effects of caffeine. However, too much sugar (including sweet coffee drinks) leads to a severe crash in energy levels once it runs out. Grapefruit juice may prolong the effects of caffeine, although this isn't certain. Note that grapefruit juice can have dangerous effects on many other medications, so check those warning labels. If you take echinacea, theophylline...

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Write a summary of the previous text in Indonesian:
Konsumsi kafeina dalam jumlah sedang. Atur waktu konsumsi kafeina. Pahami interaksi kafeina dengan obat dan makanan. Hindari efek putus kafeina (withdrawal) dan gangguan tidur. Pertahankan berbagai kebiasaan yang menyehatkan.