My take on this subject is that if you are writing instrumental music-then listen to the masters of the genre that you are trying to compose in and steal their ideas. Every genre of music has it's cliches and 'chestnuts' so to speak but they are there for a reason,you have to see what worked in the past and has stood the test of time. Certain chord progressions have been in use for hundreds of years because they are practical and pleasing to the ear.(Bach)
If you are having trouble connecting song structures,perhaps you need to simplify.
(Stealing ideas) Is a tried and true method. If you are writing blues instrumentals,you would study 'Hideaway''The Stumble' and borrow turnarounds/licks because those are established classics of the genre. If you want to write classical music for guitar well, you would study something like Bouree,Instrumental shred,borrow from Satch,Vai Gilbert,Malmsteen... if you write jazz fusion listen to Weather Report etc. etc.
My point is that once you in a given style,half the work is already done,you just have to put your original spin on it. If what you're writing doesn't HAVE an identifiable style then that is something that needs to be addressed. My 2 cents.
I think "borrowed ideas" would be a better term don't you think? Because you are not actually stealing stuff from one song and putting it into the other, leaving the first song without it.
I don't think it's stealing at all, sure you can borrow or copycat some progressions or whatever from a song you like, but bear in mind that two factors should be taken in consideration when doing this:
1.- Be original, if you are going to borrow a progression at least try to make it your own, add a little something to it, harmonically, melodically and in terms of timing (or meter) maybe a chord tension, maybe in a different key, different timing, throw in a substitute dominant into it: Nobody owns chord progressions, but you can make them your own in your compositions.
2.- First, try to write your OWN music without copycatting anything, sure if you make some harmonic analysis on it you will surely find the most common of progressions in the world, but at least it came out from YOUR inspiration and it came straight and naturally from you, thus being authentic to you.
Remember what you write music for, you don't write music to get people to like it, or like you: you write music to develop spiritually healing tools for yourself which then other people can find useful as healing tools as well.
Good Luck and happy writing.