“We must pay the most careful attention, therefore, to what we have heard, so that we do not drift away. For since the message spoken through angels was binding, and every violation and disobedience received its just punishment, how shall we escape if we ignore so great a salvation? This salvation, which was first announced by the Lord, was confirmed to us by those who heard him. God also testified to it by signs, wonders and various miracles, and by gifts of the Holy Spirit distributed according to his will.”

Hebrews 2:1-4

1) So that we don't 'drift away'. We are more likely to 'gradually' put distance between Jesus and ourselves than to do it abruptly. This can happen when we -

2) Ignore this great salvation. Every day we have opportunities to 'pay attention' to Jesus, live as if we're already in His Kingdom abiding by His ways, or we can ignore our knowledge of scripture and the nudges they may give our conscience. 

I was teaching a young person how to snorkel in open ocean once, a couple of miles from shore and off a boat that took about 6 of us out to see beautiful reefs. I was trying to keep my eye on the student and never lose awareness of the boat. Make sure I could stay close enough to drag them back on board if need be. Skin diving along the reef with beautiful marine life and clear water, I fortunately succeeded at getting us all back safely. But I'll never forget that fear of letting the boat get too far away. In a moment of pleasure watching fish, the boat would gradually get much further away than I thought, and I can still imagine how easy it would have been to indulge in the reef and ignore the boat until it could be totally out of sight. 

Disciples don't usually swim away from God as fast as we can. We get attracted to something else and gradually drift away, ignoring the currents and tides that are sweeping us further out to sea.

Don't ignore the Lord and drift away. Stay as close to the Captain as you can.