I am not good at relaxing

Jesus said, "Come to me, all you that are weary and are carrying heavy burdens, and I will give you rest. Take my yoke upon you, and learn from me; for I am gentle and humble in heart, and you will find rest for your souls. For my yoke is easy and my burden is light" (Matthew 11:28-30). Despite Jesus clear instructions and invitation, I find it hard to relax. At times I feel like relaxing is somehow a waste of time (which, by the way, I am pretty good at doing). I feel guilty that there is something I should be doing, someone I should be visiting, somewhere I should be.
Perhaps, despite my faith, I have trouble believing Jesus meant what he said. "Deny [yourself], pick up [your] cross and follow me," (Mt. 16:24) you betcha. "I will give you rest for your souls," um, well that just sounds too good to be true.
What is certain is that Jesus worked and rested throughout his ministry. He made time to be with the people, but also to find a quiet place for himself. Jesus went to weddings and feasts and never once seemed to think any of these things was a waste of time, was time he could have spent doing something else more productive.
I know I am a better pastor when I take my days off, but sometimes that is hard to believe. To try to convince myself of this I went on a retreat last October where they drilled it into my head that Sabbath-keeping was time well-spent. I even made a rule of life with sabbath-keeping (read resting) activities featured prominently. Despite all of that, I still feel, well, guilty about taking time off.
I think I need help and I am convinced only Jesus can provide that help. If only I could get over my unbelief.