Hi K.,
At 21 months, a toddler is seeking independence, yet, their is that lack of impulse control. Even once a young toddler seems to understand that running in the street may be dangerous (because he's heard it 20 times over that past couple of months), it will be a while longer that he will have the control to stop himself. You must carry through...and safety should come first.
These skills are learned and it takes many, many months of repeated instruction from the caregiver.
Remember that toddlers have short attention spans. Some have more difficult temperaments. Many parents feel inadequate when trying to discipline a toddler that is more "spirited".
Give your toddler positive attention when you are happy with his behavior. For example, "We looked at the book together."
*Do this at least a few times a day!
On the other hand, use positive discipline, too. When a child was in the swing at the playground and it was time to go, I would tell the parent to use the 3 minute warning. Then, after a few minutes, it was up to the parent to walk the toddler to the car. Most toddlers would scream! It's ok. Explain that it's time to go home. So, pick up your toddler and keep walking.
Think of it this way, when you leave your driveway, your toddler must be buckled. You can say, "When you are buckled, we can go see Daddy." So, when it's time to leave the park (or backyard), assist your child.
Use the above example as a teachable moment: "When I pick you up (from the swing) - we will go home and eat that delicious watermelon..."
Sharing is a bit the same, it takes alot of role modeling. When I work with a group of parents, I will instruct them to say the following, "I know you have the blue truck. Now, it's time for Jimmy to play with it. I will help you pass it to Jimmy." (Some parents think the word "share" is too hard for their child to grasp). Whatever word you choose, be consistent with the word or phrase.
A (YOUNG) toddler is thinking, "I own that truck and all the trucks here."
Offer a short explanation when disciplining. It takes a toddler a long time to comply or share. Be kind, firm and loving! And, know that it "seems" like a long time before your hard work pays off.
Most toddlers are happiest when they are on the go, until you come forth with some healthy limits!
Healthy discipline is well worth it as children get older...
Warmly,
Kristen
Parent Educator