Simple rule: NEVER
include a card in your deck that, if played against you, is likely to destroy you.
This existed even before mindgate, with a small variation: NEVER
play a card that, if played against you, is likely to destroy you.
Example: don't play your Lobo aginst Decay, don't add MFlayers to your forest spirit deck (you are not Elidnis
), careful with Discord in you mono entropy, etc.
There are exceptions, but you'll find it easier to stick to the general rule for a while.