How you combine sentences is an aspect of voice. Now I know some writers want voice to be spontaneous expression, and sometimes it is. But if a passage isn't working, if it feels jagged or incoherent, look at the way you've put together the sentences. That is, be conscious, not self-conscious.
What you put together in a sentence is what readers read as going together, and they'll subconsciously try to come up with a reason these go together, or at least mentally read them together as a single thought. So this process of putting together sentences shouldn't be arbitrary. You don't have to plan every sentence, of course-- most of us can trust our instincts most of the time-- but do be aware that you are making meaning by combining certain elements, and as you're reading over, see if that's the meaning you want. (Rhythm also is a factor here-- "jaggedness" might be the result of combining the wrong elements so the flow is interrupted. You might or might not want that. Do you? You will sometimes, but not always.)
So here's a string of sentences that can be combined various ways (coordination, subordination):
Helena sailed into the ballroom (the verb, btw, is important-- she could sail in or glide in or stroll in or stalk in or stroll in, and each tells us something different about her and her attitude at the moment).
She looked around the crowd.
She came to me.
She bestowed an air kiss on me.
I started to say something seductive and witty.
She moved on to another party-goer.
She kissed him the same way.
I felt rejected and cheated.
Now one of the marks of the amateur (another!) is inappropriate sentence combining, where elements are linked presumably because they came out of the pen in that order. This is what I sometimes see in submissions:
Helena sailed into the ballroom, and she looked around the crowd, and she came to me. She bestowed an air kiss on me, and I started to say something seductive and witty. She moved on to another party-goer, and she kissed him the same way. I felt rejected and cheated.
The problem with that is that the elements are put together without regard for what belongs together, and without the coordination or subordination that adds meaning (like cause/effect and contrast). It's all just linear: This happened and then that happened, and then that happened. ("And" is a useful connector, but it really just implies addition, and that doesn't add a lot of meaning.) So let's move beyond the linear and simply chronological. Also notice that even chronologically, not all sequential events belong together. For example:
She moved on to another party-goer, and she kissed him the same way.
The moving on happens before -- "is happening," that is, it's a progressive event, like "crossing the street." It takes more time than a single-moment event, like kissing. Not a big deal, but because of the time differential there, I don't know that I have them linked with "and" (or linked at all).
But most important, the meaning of this passage isn't the sequence of events, or rather, the sequence only matters because some of the events are cause-and-effect, and cause-and-effect requires sequencing. But the cause-and-effect conjunction isn't "and;" it's "so." And the contrast conjunction, where you want to show a conflict between two things, isn't "and" but "but." I'd look at each clause and think about which one causes another, and which is in contrast to another, and experiment with the pairs in the same sentences. (That isn't always best-- if the second clause is an important action or conclusion, you might try it in a sentence of its own.) AND... some of the independent clauses can be reduced to dependent clauses if they are in fact sequential or simultaneous, if "time" is the most important link to the next event. So maybe-- and as I said, I always experiment to see which assemblage conveys my meaning better.
As Helena sailed into the ballroom, she looked around the crowd. She came to me and bestowed (notice we lose one of those many "she" words, good) an air kiss on me. I started to say something seductive and witty, but she (just? had already? was already moving?) moved on to another party-goer. When she kissed him the same way, I felt rejected and cheated. (Or I might say, Then she kissed him the same way, and I felt rejected and cheated. Not sure.)
This shows more of what's really going on, not just the events but the meaning too. Helena is special to him, but he's not special to her, and we (and he) learn this in this paragraph.
If you fear that your passages are too choppy or too unsophisticated, if you're told by an agent or contest judge that you're not showing the emotion, see if you are overusing "and" as a conjunction between sentence elements. (Transitions aren't just conjunctions, of course, but here they happen to be.) (BTW, you might be told, if you use a lot of transitions, that you're explaining too much. That is one of the major differences you see in modern litfic-- there's often not much transition or conjoining, so the reader determines how to relate the events or ideas. I err more on the over-explaining side... how surprised are you? :) The major coordinating conjunctions are: and, or, but (or yet), so, for (because-- in the US, we're more likely to go with "because"). The major subordinating conjunctions, well, there are too many to list, but these are the words that start dependent clauses: As, although, when, beside, because, after-- many are time/space connectors, showing how this relates to that in time or space.
These lists reflect the most important relationships between events and thoughts and actions and such:
Chronology, Addition and sequence (and, moreover)
Causation (so, for/because, therefore)
Contrast and conflict (but, yet, however, although)
Transitional words do more than just smooth the flow of the passage (though they certainly do that-- supple prose usually depends on transition). They show the relationships of events and actions and thoughts, going beyond a mere collection of sequence into a textured skein of causation.
And they also help to make a paragraph a paragraph, which is something I want to explore in depth in the future.