As Rails is a framework for constructing web sites/applications, I think it would help you to have "an idea/web site" that you can use as a basis for your training/learning - that way you should be able to keep the momentum, when things get tough!
Remember you can work on the 3 main areas (Models, Views, Controllers) a little at a time. I.e. You can construct your tables/relationships (aka models) before you construct any views or controllers - this way of working can help to boost your confidence with Rails.
If you are working on your own then I'd recommend spending some time (upfront) on a few sketches that outline the major paths/interactions/screens that you expect the end user to traverse.
A lot of stuff(blogs) has been written about Ruby/Rails much of it is a rehash of existing material - find 2 or 3 sites that you like and stick with them. One of the better ones, IMO, is www.railscast.com which is owned by one of the moderators on this site.