As a parent, you are in charge and only you can decide what limits will work for your family. Very young children (under three) are not able to reason about things. They do not have enough experience to know what is safe or appropriate. They need their parent to take control, particularly when behaviour is dangerous and they need to know that we mean it.
Once you have decided what the limits will be, remaining consistent is very important. When we provide children with reasonable and consistent limits, they feel secure. Young children need to test limits to find out where they are and if they are firm. If a child is allowed to do something one day and not the next, this can lead to confusion.
That is not to say that this is easy work. Early parenting tends to go hand in hand with exhaustion, and tiredness can erode our resources. Sometimes it can feel easier just to give in, and even though your child's tantrum or tears may stop, inside their world may have been rocked because they have received the signal that limits are negotiable. The more consistent we can be the faster our children will adapt to the family's limits.
Children like to be able to predict what is going to happen and how you will react. Building a routine for your child around the natural rhythms of their day can help with this. For example, regular play time, meal times and sleep times. There are things that you can do which provide cues to your child to let them know what is coming next e.g. a story after bath-time signals bed-time.
The limits you set and the routine you establish will change as your child grows and develops. Adjusting in this way communicates your growing trust in your child's capabilities and this will give them the confidence to impose their own limits on themelves as they grow up.
You can find more information on setting limits can be found here