Are there any Sifre Musar that give advice on how to become more patient? If so, can you bring a few points on how to do so? Please cite sources.
I suggest Gateway to Happiness By Rabbi Zelig Pliskin
The lesson in patience which I still recall - 25 years after having last read - it is the following:
Imagine you're standing in line. A long slow moving line. Seemingly impossible not to become impatient when standing on line. Right? You simply stand there impatiently wishing it would speed up.
Now imagine that it's a line to the crematorium! Suddenly you're praying that the line will take forever. You'll even let people push in ahead of you if they so wish. Oh! So it is possible not to be impatient when standing in a slow moving line.
Conclusion: it's our perspective that makes us impatient - and we do control it.
This is one of the rare occasions when he uses gruesome examples, but it sure is effective. Gateway to Happiness is a book worth reading. So are his other books.
Disclaimer: I have no connection to Rabbi Zelig Pliskin, though I have met him and thanked him for his advice.
Notably, the Orchos Tzadikim (which is probably the classic sefer on middos development and has chapters for each character trait) does not have a section on patience. In the first chapter he writes:
Orchos Tzadikim Sha'ar Haga'aveh
ועוד הגאוה גורמת שלא יהא סבלן לסבול עול הבריות ואין צורך להאריך בפחיתת מי שאינו סבלן כי ידוע לכל
Furthermore, pride causes one to lack patience in bearing the yoke of his fellow man. And it is not necessary to elaborate upon the defectiveness of impatience, as it is acknowledged by all. (Feldheim p. 33)
The author apparently felt that it was unnecessary to speak about patience; however, there is a hint here that you can perhaps work on patience by working on pride.
impatience can sometimes be a good sign. it can mean you value your time and as Rabbi Noach Weinberg said: "Killing time is spiritual suicide". In his 48 ways to wisdom #1, he suggests to not waste a minute of time. Ex."Memorize pieces of wisdom. It will give you something to learn as you walk down the street or wait in line at the supermarket"