You're not the only one who has gotten yelled at by Lightening thief haha . Being the kiss of death guy sucks, i've been there, you'll get better as you play more games (I hope). Knowing your role definitely helps (playing front or back) and dont forget to take it easy! There is over 200 seconds in a match, no need to rush to make something happen.
I would recommend looking at Brett's second impact, it is very helpful to newcomers and I think it will be of use to you. Perhaps you could even send him one of your replays to look at.