Suck it up and do it. Work with your coach to make sure your technique is good then just swallow your fear in a game and give it everything. Nothing builds confidence like putting the opposition second rower on his *** so just line him up and knock him into next week. If it doesn't work think about what you did wrong then try again
Get yourself in a scrum and "feel a man"
Aim for there hips hold on tight on put all your weight on there legs.You are going to get hurt but isnt that why we play rugby?
find a bud. wrestle and tackle each other. it worked for me after I broke my collar bone.
get someone to tackle you repeatedly