1. Make a list, post it on the wall and release it all from your mind. Work on one thing and you will have the pleasure of crossing it off. I use a "grease board" I got at Goodwill.
2. Do the body work, fill the holes, drill new as needed and get it painted, that will REALLY motivate you. You will see how neat it is going to be. Doing something big will do it.
3. Everybody loses interest and then regains it. Take a rest. If there are other things bothering you, work them out. Clean up the area. Put tools away. Label all the parts and put them away so you can't see all the parts. Get a roll around chair and a table and sit there where you can see your beauty and have a coke. Then do the list as you want to. You will cross things off and erase them and add new things as you "explore". It's all normal what you are doing and feeling. Don't buy a bunch of new parts until you really need them. There are two other times people buy parts: When they first get the truck and when they need motivation, both buying sprees are to be avoided.
4. We feel your pain(t).