Sorry that my answer isn't multitradition, but I can answer biblically speaking.
The Lord tells us to pray:
Ephesians 6:18 NIV
And pray in the Spirit on all occasions with all kinds of prayers and requests. With this in mind, be alert and always keep on praying for all the saints.
Then Jesus told his disciples a parable to show them that they should always pray and not give up.
And offers help in how to pray:
Romans 8:26-27 NIV
In the same way, the Spirit helps us in our weakness. We do not know what we ought to pray for, but the Spirit himself intercedes for us with groans that words cannot express. And he who searches our hearts knows the mind of the Spirit, because the Spirit intercedes for the saints in accordance with God's will
And tells us WHY to pray:
Zechariah 13:9 NIV
This third I will bring into the fire; I will refine them like silver and test them like gold. They will call on my name and I will answer them; I will say, 'They are my people,' and they will say, 'The LORD is our God.'
So, what if you don't pray? I don't think it's a sin or you'd lose salvation because of it, but you will be a better person with it. It's a bit of stretch, but you could say that it's similar to adultery -
Matthew 5:28 NIV
But I tell you that anyone who looks at a woman lustfully has already committed adultery with her in his heart.
But we have eyes to see and minds to think, thus we've all committed adultery (some more than others). However you will not lose your salvation, you'll just have a better life if you keep the eyes from wondering.