Do you have a daily routine?
It can be hard to put a good routine into practice, but once you have it going, it makes it a lot easier to make good choices. Once you've got it going, it sort of puts good choices on auto-pilot: you do the right thing out of habit, without having to dig down and find the self-control and willpower to resist temptation.
How are you praying?
Don't get me wrong: it's really important to call on God and ask him to help "make us straight". And that isn't whining, so you definitely don't have to feel bad about doing that. But if that sort of prayer is taking up most of your daily prayer time, it might be worth including other sorts of prayer. There's a list of the five "forms" of prayer here (pdf). If you're not doing it already, I'd also suggest trying to do some sort of daily spiritual reading. Even just five minutes each morning with the Bible, or Lenten meditations, or another spiritual book.
Are your goals realistic? Are they the "right" goals?
Last year, I had an awful Lent (it actually sounds like it went about the way yours is going). Looking back, I made two major mistakes. The first one was that I tried to do too much. Even when I made my goals, I didn't think I would be able to achieve them, so giving in felt inevitable. I ended up spending a lot of Lent just feeling guilty. Not ideal.
The other mistake I made was that I made the wrong goals. For example, I was skipping prayers, so I resolved to pray more each day. I was even specific: I was going to pray the rosary every day during Lent. It was a good resolution, but I didn't look back to see why I wasn't praying: what I should have done (again, with the benefit of hindsight) was give up one of the "distractions" in my daily life that was keeping me from prayer (e.g. computer/tv or sleeping in).
There's still a lot of Lent left this year, so it might be worth it for you to take a day or two, maybe this weekend, "off" and try to re-evaluate. Maybe pick one thing to focus on. Pray about it, and try to understand why you haven't been successful so far. Then make a new resolution to focus on during the next four weeks. You'll have to figure out what works best for you, but it should ideally be a concrete action that you will do at a specific time each day. For example: As soon as I get home from work, I will go for a walk around the block. Or: Right after dinner, I will pray a decade of the rosary. Especially if you are struggling to follow through, it might be easier to have an "I will" goal than an "I will not" goal.