My doctor told me to start at 25mg and go up by 25mg every 1-2 weeks, how do I know when I have the correct dose?

My doctor prescribed me sertraline about a week ago and told me to start at 25mg per day and go up by another 25mg per day every 1-2 weeks. Starting at 25mg and slowly making my way to 100mg per day. How will I know once I’ve reached the correct dose? Especially since it takes 6 weeks for full effects.