If you are learning a language, and it is not fun, then you're doing something wrong. See what can be changed.
When your brain thinks that some word is not necessary for your nearest activities, it tries to forget it as soon as possible. Even an adult needs motivation, and two most common kinds of motivation when learning languages are necessity and fun.
Necessity. Make use of the newly learned words. Many learning techniques are based on this. For example, the Pimsleur method assumes that you start practically using the newly-learned words since the very lesson #1. If I know that tomorrow I'll be going to a local shop (in a foreign country) to buy a pancake, my brain will see the reason to remember this word.
Perception. Separate speaking from reading. Some people don't remember well the things that they see (including the flash cards), but instead they better remember from hearing. We don't know what works for you, but if you never try you never know.
Important things go first. Don't abuse the dictionary. Try learning ready-made phrases first. I've seen people who know how to say e.g. "elephant" in a foreign language, but failed to construct a simple phrase (with or without this word).
Again, when being in a market in a foreign country trying to buy an elephant, I would prefer myself being able to say,
"I'd like to buy that big gray thing; no, not that one, a bigger one please" (note, all words in the phrase above are usually learned during the 1st month of study), instead of boringly pushing useless "elephant", "giraffe", and "alligator" in my brain hoping that it becomes useful one day.
Fun. Also, don't simply give up with the flash cards, try some other ways using them instead. From personal experience, I found drawing them myself (yes, on paper) works better than my previous attempt to use flash cards in computer.
Find your own fun. All people are different, so experiment to see what works for you better.