At this stage, with your child's growing awareness, his emotional development too is happening rapidly. As a result of this surge, he is often unable to control his impulses. It will take time for him to understand the way of keeping his impulsive instincts in check.
What you need to know
This phase of your child's development that begins at this age and rounds out at age 4, is the period of time when he's practicing and learning delayed gratification and impulse control. It's normal for them to scream, lash out in anger and get easily excited. However, as children approach the age of 4, they should be developing improved ability to manage their impulses, and hitting and tantrums should subside.
Demonstrate rather than verbally instructing
As babies grow into children, it is a critical time for you to teach your child skills to begin learning how to control their impulses. I would suggest that you should show, not just tell, your child how to control their impulses. If a 2 year old throws a crayon, Mommy should ask their child to pick it up. When their child refuses, as they likely will, Mommy should put their hand over their youngster's hand and move the child through the motions of picking up the crayon. It is always been noted that it is important to "always follow it with praise."