oh yes very true.
i used to think that adding some shred guitar in my arsenal was an impossible goal for me. but lately i found out that was possible when i took all the time i wanted decreasing my speed and slowly focusing on getting every note hit and sounding out. now as i go faster, i managed to sound like i was playing some fast stuff. of course it ain't that perfect now, but hey, im getting there!
you also need to work out a plan on how you wanna fruitfully spend your time practicing guitar. remember, it is not about laboriously working your way to achieve greater heights overnight. i remember seeing from a marty friedman video on how to do that. basically, you will need to set aside what you are gonna do when you practice. and the key is to focus on what music you like to play. like you will take the first ten minutes to do warm ups and those finger exercises, then you'll spend like 20 minutes on a technique, then 30 minutes on a new one and the rest of the time remaining to learn a new song and stuff.
mine would be something like this:
5-10 mins: Left and Right finger warmups, petrucci's rock discipline alt picking exercise in different keys and different picking strokes.
20-30 mins: Technique practice and revision. This will be on techniques im already familiar with (gallops, alt picking, string skipping etc..)
30mins-1hr: Technique practice (new). This will be on techniques, preferably one, which you are new to or need more revision on. mine is currently sweep picking.
1hr - 1hr 40mins: Song Practice (new). This will be on a song you wanna play which have never played before or which you need more practice in. It need not be the whole song but it can be in the particular area you wanna refine or practice.
1hr 40mins to 2hrs: Song Practice: This will be on a song you already know but still wanna practice to maintain it.
yeah, thats 2 hours of practice for ya. you can alter timings or put in whatever you wanna practice, scales, harmonization, theory etc. although it is inevitable to deviate from the above mentioned example of how to devote yourself to practice (including me), you will progress much more in the long run if you stick to it.
and finally, DON'T KILL YOURSELF. the last thing you need are broken or strained limbs and a big blow to your muscle memory and bad habits embedded as a result. you do not want that. and that can be avoided by simply not any pain practice or going over your limit.
my 2 cents.
cheers
ive hoped ive helped