It's a perfectly reasonable question, if your thinking of altering something you spent actual money on rather than pulled from a charity shop then your bound to be aprehensive.
So to start I always divide mine into two piles the ones that I'm hoping to salvage, this includes shrunken tee shirts, mr Knitwit jumpers, and old jeans. These are what I consider throw away projects, things that if they don't work it doesn't really matter because chances are they'd end up in the bin anyway.
Then there's the alterations, things that just don't work right now! The things that I like but I just don't seem to wear for some reason. I like to make these item reversible so they can be used as they were originally intended!
This skirt used to reach mid calf, it wasn't maxi and it wasn't midi. It was however filled with sentimental value (my dad brought it for my mum)
Now I knew I didn't want to bin it, I love the lace and the waistband, but I also knew I didn't want to cut it incase a 30/40 year old Frankie still wants to wear this skirt but would appreciate more coverage!
That's why this skirt has a 30cm hem. No seriously on the off chance longer poofy skirts are back in fashion all I have to do is unpick my hand sewing and I'm sorted!
I guess what I'm trying to say is, it doesn't all have to be so drastic, on refashioning program's and blogs we see them hacking away at garments. Well the thing is you don't have to, embrace deep hems! Keep the sleeves you didn't want one the off chance that maybe one day you will! Make the collar detachable and you'll find you can really turn your wardrobe into a workhorse!
And then as you gain confidence in what works you can start to take bigger risks!