There's no such thing as "translate to kanji"; kanji is a system of letters. What you're actually asking for is a translation into Japanese, and what you're asking for is a sentence, so it would be a mixture of kanji and hiragana.
I'm almost always more impressed by nice English calligraphy than some random kanji from a computer font. I'm sure you could easily find someone in Sweden to give you a calligraphic representation of what you're asking for in Swedish. It would be much more personal, artistic, and guaranteed to be well-crafted.
Now, with that being said, I'm not very good with Japanese, so take this with a grain of salt. Don't go tattooing something to yourself that you heard from a 下手な外人 like myself without verifying it first. But I think the most concise phrase you're ever going to get with a meaning similar to what you asked would be "諦めるな" ("Don't give up").
Again, though, and I can't stress this enough, if you get that tattooed to yourself from a computer font, it will be just as tacky as if you wrote "Never give up" in Times New Roman and made that a tattoo. Remember, these are letters, and computer fonts are almost always functional, not calligraphic.
I also want to stress that if someone who doesn't know how to write Japanese etches that permanently into your skin, chances are very high that they're going to make mistakes, and that would look silly and clumsy. Just imagine someone tries to write "Never give up" as a tattoo, but accidentally writes the letter "e" backwards, or adds a curve that makes the "v" look like a "u", because they never learned the Latin alphabet.
Just to emphasize this point, I highly recommend you either: (a) get this in Swedish calligraphy; (b) work with a tattoo artist to come up with an artistic representation; or (c) don't get a tattoo.
But it's of course your body, your choice.
