If you are not doing the reps on the machines or free weights with a full motion in each one, you could be wasting a lot of time and energy. For example a curl for your arms should use the whole extension of your arm, not a half way down and back up move. Unless you are very advanced and have a reason for that shortened rep.
A pull up on a bar requires the same. You should be going all the way down each rep. If your last one or two are not full, but the prior ones were that is ok. But cheating to get more reps when you are training is not helpful except on the last rep or two.
Also while we are at it...rushing the set is not helpful either.Take your time make the most of every rep and each set you do.
That will make it all worth while in the end. Progress!