‘Сейчас’ and ‘теперь’

Both adverbs can be translated into English as ‘now’, but actually they are not absolute synonyms in Russian. We use ‘теперь’ when we want to emphasize that now the situation is somehow different from the past, the contrast is implied.

Мне 18 лет, теперь я могу голосовать! = I am 18 years old, now I can vote! (before I couldn’t)
Раньше я боялась собак, а теперь очень их люблю. = I used to be afraid of dogs, but now I love them very much.

Also ‘теперь’ shows that something happened as a result of something that was mentioned before.

Я забыла кошелёк дома, и теперь я не могу заплатить за билет. = I forgot my wallet at home and now I can’t pay for the ticket.
Я купил машину – теперь я могу забыть о метро! = I bought a car, now I can forget about the subway!