Hi Peter -
You have posted several pieces here at PS, and I have listened to a few of them. You seem very young, enthusiastic, and seem to thoroughly enjoy writing music. Keep that enthusiasm, as it will carry you through when things don't seem to be going so well.
Writing music is one of the most rewarding pursuits I can imagine, but what makes it that way is it's nearly bottomless depth of meaning, emotion, and inference.
You seem young because your music depicts a very ordered, secure, and predictable world. Every phrase (except for mm.33-42) is four bars. Nearly every phrase starts with a G major chord. [The harmonic progression is the same as Pachabel's Canon, by the way.] Your music would be more attractive if you varied the length of your phrases. Look at the music of Mozart and Haydn, for example. See how they use occasional 3, 5, 6, or 7-bar phrases. Try to determine why. See how they set up a cadence and then elide the ending of one phrase with the beginning of another. If all your phrases are the same length, and go to the same place, people will stop listening. You can imagine what it would be like listening to someone speak and every sentence was the same length and said the same thing (even if the words were different).
Another phase which betrays your age is your impatience. You seem to want to finish this as fast as possible. Brahms took over ten years to finish his first symphony! There is not a single articulation in your score, no accents or sfz's, no dots or dashes or slurs, no portamento or grace notes or double stops. You don't seem to be actually writing this for live string players, but for a synthesizer. Learn about string playing. Learn about how the bow works and how it is notated. Study the music (and string writing) of any great composer and look at the care and detail he or she takes in writing every note, every passage. String instruments are fingered so that each finger plays a letter name. F# is fingered differently than Gb (two different fingers). As a result, D and D# are played with the same finger, so you must be careful about your accidentals; you must make them tonal. For example, mm.39-42 needs to be Eb and not D#.
Pizzicato and Arco Marcato are synthesizer sounds, but a real string instrument can do so much more. Sibelius (the notation program) bundles 17 or 18 sounds into just its Violin designation. Never take the easy way out. Make a decision about every note and aspect. How many decisions does a repeat mark take? It's the same for cut and paste. Learn to question everything, and don't be controled by your tools (i.e.-computer). Think about tempo, phrase length, meter, color, as many aspects as you can single out. Think about the beginnings of your notes, the endings, the middle - orchestral instruments, unlike the piano, control all parts of the note. For example, instead of writing a whole note G in the cello mf, you could write pp arco (with a snap pizzicato in the viola) crescendoing to f tremelo in the middle of the bar diminuendoing to pp at the end of the bar, with a ringing bass pizzicato of a harmonic G at the cutoff. Look at the scores of Mahler, Strauss, Debussey, Stravinsky, Prokofiev - and look at the actual parts as well as the combinations.
You have drive, desire, and talent, but now you need to start taking the boat out of port. I don't think you would be writing music if really WANTED an ordered, secure, and comfortable world.
Best wishes and happy holidays -