Just to add something to compart1's great advice...just keep it all in perspective...presumably you are doing this for fun. If you skip a night of practice or don't get something down in the timeframe you set for yourself, it's not the end of the world. You aren't going to miss a rent payment because you didn't get something down on your guitar :).

Try to not pressure yourself...keep at it and it will eventually come with consistency. When I get stuck, I find something else I can to and still make some progress just like Compart1 suggests.