Guided tours almost always include a support van to help you all or part of the way. Be sure to check the "Included services" on the Dates & Prices tab for exact inclusions.
On self-guided tours, it's your responsibility to get from the start to end hotel each day, but you can get help. Make sure to keep the tour company's service number in case you need advice along the way. In many cases, trains, buses, or even ships may be an option on days when you don't feel like riding. Occasionally, and with enough notice, you may be able to hitch a ride in the luggage van.
More on guided and self-guided tours