Sounds like you just need to practice your basics.
I'd give up on learning songs for now and go back to the rudaments. Practice the very, very basics... finger placement, hand position, changing between chords. Work all of those with diffrent tempos, picking speed, and picking styles. (IE: 8th notes down strokes, 16th notes alterhanting picking, skip strings, etc...)
The fact is, you can't do it... that's why you practice. If you could do it from the start, you wouldn't need to practice... you'd already know how to play. Don't get discouraged that you can't do it... that's the point of practice.
I took lessons, which helped tons, but the other 6 days of the weeks I learned by studying my ass off... I stared at pictures of my favorite musicians and watched tons of videos. I took note of the angle of their wrist and fingers based on what notes they where playing. I tried to mimick it... now days you have tons of help online so don't be afraide to youtube hand placement videos and the such. Seriously, you'd be suprised at how much something minor like the angle of your wrist can hinder or help your playing in the long run.
I suggest lots of scale work. Then chords. When you can run the scales smoothly and switch between chords with ease, then go back and pick up that tab you can't play. See how much better you are.
When I got my first guitar my goal was to play songs from the Appitite for Destruction album by Guns N Roses. I bought the book first thing and every other month I'd try to play a song. It took a long time but slowly I saw I was making progress. It's always nice to have both short and long-term goals. My short term goals where the basics... learning scales, playing cleanly, etc... long term goals where complicated songs and entire tab books.
I have no idea if any of that helped.
