I will stick my neck out a little, claiming that both of your original sentences are fine by themselves, on the ground of Parataxis, though it might be safer for you to use semicolons (instead of colons) or write each of them as two sentences instead (no conjunction needed).
One well-known example is Julius Caesar's famous quote:
"I came, I saw, I conquered."
(Note that the Parataxis page on Wikipedia uses commas, whereas the same one on About.com uses semicolons.)
Here is an excerpt from Wikipedia:
Parataxis may be considered from three points of view:
- the psychological aspect,
- the linguistic means to express the paratactic relation,
- and the resulting sentence structure.
The underlying idea is that in a connected discourse, complete independence among the consecutive sentences is very rare. This observation is captured in the expression "train of thought". Consider the following:
- The sun was shining brightly. We went for a walk.
- The sun was shining brightly; we went for a walk.
- The sun was shining brightly, and we went for a walk.
- The sun was shining brightly, so we went for a walk.
In the first example, the two sentences are independent expressions, while in the last example they are dependent. However the connection of thought in the first examples is just as real as in the last ones, where it is explicitly expressed via the syntax of subordination.
Here is what About.com says about parataxis
Parataxis (also known as the additive style) is sometimes used as a synonym for asyndeton--that is, the coordination of phrases and clauses without coordinating conjunctions.
Parataxis is not rare in real English. For example,
"In the bed of the river there were pebbles and boulders, dry and white in the sun, and the water was clear and swiftly moving and blue in the channels."
(Ernest Hemingway, A Farewell to Arms, 1929)
"I needed a drink, I needed a lot of life insurance, I needed a vacation, I needed a home in the country. What I had was a coat, a hat and a gun."
(Raymond Chandler, Farewell, My Lovely, 1940)
However, as Stanley Fish mentioned in How to Write a Sentence, it's a difficult style to master,
Although it might seem as if writing in the additive style is just a matter of putting one thing after another in no particular order (how can that be hard?), it is in fact the far more difficult style to master; for the relative absence of formal constraints means that there are no rules or recipes for what to do because there are no rules or recipes for what not to do.
Or as Richard A. Lanham wrote in Analyzing Prose,
But parataxis can be a contrived, patterned, self-conscious style, one whose syntax can carry . . . an allegorical meaning of its own. It is easy to write a laundry list, but not so easy to write like Hemingway without falling into parody. Try it.
So unless you are very sure about what you're doing, it is best to avoid writing them.