The Baggies are lying fourth in the Premier League after Saturday's 2-1 home success over Chelsea.
But Myhill remembers being in a similar position with Hull, who four years ago were lying fifth in December but ended up avoiding relegation by a single point.
Myhill said: "It's too early to think about Europe. The time to think about it is when you've achieved it.
"I've played in some sides which had unbelievable starts to the season in the Premier League. It happened at Hull.
"Then all of a sudden you can't buy a point. We have to carry on the way we are going. If you take your eye off the ball in this league, you will struggle."