Rowing a boat can be hard work. If you've got a long way to go, it doesn't hurt to occasionally allow your momentum to carry you along while you take a break from the oars. This is true with rowing a boat, and it is also true with life.
Jesus worked hard (John 9:4), but He also succumbed to weariness and sought opportunities to rest (Mark 4:38). After the twelve returned from the limited commission, Jesus "said to them, 'Come aside by yourselves to a deserted place and rest a while'" (Mark 6:31). I remember an older Christian genuinely scoffing when I told him that I was going on vacation. His idea was that the work of the Lord never stops, and neither should a preacher. Well, if the Lord saw the importance of resting, there must be something to it. I continue to take my vacations "guilt-free."
However, one never takes a break from being a Christian. Jesus and His disciples may have departed to a deserted place, but they didn't get to rest. "And Jesus, when He came out, saw a great multitude and was moved with compassion for them, because they were like sheep not having a shepherd. So He began to teach them many things" (Mark 6:34). There was a need for rest, but an even greater need presented itself - lost souls hungering for the gospel needed to be taught.
Opportunities can present themselves when we have something else planned. Like Jesus, we need to have the presence of mind to make the wise decision, sacrifice our personal interests (needed rest), and meet the greater need.
The Christian race is a marathon. We are in it for the long haul. Take care that you are not burning out and falling by the wayside.
"For you have need of endurance, so that after you have done the will of God, you may receive the promise" (Heb. 10:36).