This Is How We Do ItThe Worst Mistake Heroes of the Storm Players Make, and How to Avoid ItThis Is How We Do It - RSS 2.0
In a similar manner, if a battle is going poorly, and your team mates are starting to fall back, and maybe you're a squishy assassin that was left in the fight, you've taken a lot of damage, and you see the support of your team return and heal you or put a shield on you... that is not a signal for "dive back into the fight!" That support is returning to offer what he can to help you get away with your life. Don't throw that life away - not unless you'll make a great trade.
Pick your battles
Good players only risk dying when there is something worth risking their life for. So often, the beginning of a game that features a central watchtower sees the first 50 seconds consumed by teamfighting uselessly over that watchtower. Yes, vision in this game is important, but you can take back a watchtower 30 seconds later without incident. Having vision in the first minute of the game isn't worth fighting over. There's little information that you'll glean that early on that will help your team win. What's more important is to lane - to not miss out on any laning XP. It's fine to go for the watchtower; it's not fine to trade repeated deaths for almost a minute while minions are dying in other lanes with no one on your team there to soak.
Similarly, with objectives - yes objective are important, but that doesn't mean you have to kill yourself over them when you're outnumbered or outmatched. The #1 rule about picking engagements is: Don't pick unfavorable engagements. This rule doesn't get thrown out the window over objectives. If your'e playing Cursed Hollow and you see three enemies at the tribute, and you're alone, don't go in there. Maybe your thought process is, "I'll stall them." Sure, maybe you'll stall them - and then you'll be out of the game for a longer period of time than you delayed them. Your team can't keep feeding in people one at a time, dying in order to stall - it takes a few seconds to get the tribute, and it takes much longer than that to respawn and march back over to the tribute.
Along the same lines, if your team is level 9 and the enemy is level 10, you cannot contest an objective. Don't even bother trying. They will be able to use their Ultimates, and you won't. Your time is better spent trying to get to level 10 as quickly as possible so that you can be on equal footing for team fights. The only way you can win a team fight when the enemy has Ultimates and you don't is if they screw up massively - and any plan that relies on the enemy being incompetent is a bad plan.
Let's reiterate - it's okay to die, as long as you make it a learning experience. If you see that you're the person on your team that has the most deaths, try to play less aggressively. If you're new to a hero, you'll get accustomed to how easily that hero dies and what the right balance of aggressive versus careful behavior is. It's about learning when it's safe to be aggressive.