At my last lesson my teacher and I went over chord progressions. He taught me how to figure out how to stay in key, and what chords would go where. I understand how to figure that out, but he wrote a formula down to figure out when to put minor or 7th's, and I don't really like the sound it gives. I'll use the key of C as an example.

Now the chords that you can use to stay in the key of C would be:

C- D- E- F- G- A- B- C

But my instructor told me that all progressions should follow this formula...

M-m-m-M-7-m-diminished-
7-7- 7

M=major
m-minor
7-seventh
And when it says m with a 7 under it that means minor or 7.... The sevens should be under the minors, but it didn't show up how i typed for some reason...

My question to you guys is, does every progression have to follow this Major-minor formula? The seventh chords just dont seem like they fit too well..
"The object of war is not to die for your country, it's to make the other bastard die for his" -General George S. Patton
That's the way the chords are structured in the Major scale. It's not a definite and good sounding progression. A progression would be like I-V. Or IV-vi-iii-I.

And the 7th chords fit just fine. But it's all about use to get it to sound good. A G7 chord sounds good practically every time it's used after a C (to me anyways). But a Emin7 doesn't really fit with me.
your formula from your teacher is for diatonic chords ( chords that naturally occur in a certain key )

Try using chords that use the same string sets. i.e. chords on the G, B, and high E strings.
Do you mean chords that have pivot points? Like going from Am to C, they both share the C and E notes?
"The object of war is not to die for your country, it's to make the other bastard die for his" -General George S. Patton