In many multiplayer formats players play together as a team. However even if you share a turn, like in two-headed giant, any time a card’s text refers to ‘you’ it means you and just you. Effect like these are not carried over to affect other players or permanents controlled by other players.
For example, if your have a Tempered Steel only your artifact creatures get +2/+2, not your teammate’s. When Bountiful Harvest resolves you will be the only player that gains life and you only count your lands, not your teammate’s.
Today’s Rules Tip was submitted by Fabian Peck, a level 3 judge from Melbourne, Australia.