Okay, I know that writing lyrics is difficult. I struggle all the time. But one of the worst things a lyricist can do is give up completely on a song.
If you are tempted to give up on a song, don't. Put it down and leave it for a while. However long you like, an hour, a week. Months, if it helps. I've done that. The longer the better really, and I'd probably leave it at least three days to be sure. Then, when you go back go it, take out what you really like, and leave the rest. Re-write the song, and then see what you think.
Once you have written a song, never just leave it. When you have written it, leave it for a week. Then go back to it and see if you still like it. Re-write what you don't like and keep what you do.
This may work for some, and won't work for others, but it works for me. I almost always write about how I feel. When I feel pissed off, I write about it. When I feel like I've been drinking tequila out of a tornado, I write about it. If I'm more than ready to cry, I write about. And something to bear in mind is that if you are writing about your emotions, the line doesn't have to make sense to an outsider, as long as you know why it's there and what it means. It may look cryptic and impromptu, but if you are writing about you, it doesn't matter if that one line doesn't link with the rest of the song.
As a songwriter, remember this; remain tasteful and respectful, and no subject is out of reach. You can write about anything if it isn't offensive. For example, you can write about the death of a famous person, and write about the tragic circumstances of their death, as long as you don't start going on about how nobody liked them until they were dead. I have written songs about the 27 club (every musician should really know what that is, but if you really don't then google it.)
You don't have to finish the line! That is the power of music. You can end it a couple of words before the end of the line, as long as you know what you mean. This is good for sexual innuendos (eg, 'I could only think of you, and all the ways that we could...').
This is one thing I do, and people think its ace. All you need is a shit, throw-away line that means bugger all, and google translate. Pick a language you like. Spanish works well for this, because Spanish is a stunning language if you want something mellow, German is good for an angry sing, and French sounds quite sexy. Then tap your line into google translate and all of a sudden, you can say shit, bu it's in another language. The two benefits of this are primarily that nobody understands what you are saying, and also that people think bilingual musicians are awesome.
That's all I can say for now, but I hope it helps with future dilemmas :D