Don’t take sets to the point of failure—where you absolutely can’t perform another rep. You should never get to where you’re turning purple and screaming like you’re getting interviewed by “Mean” Gene Okerlund before WrestleMania. Most of the time, you want to end your sets two reps before total failure. Not sure when that is? The moment your form breaks down, or you’re pretty sure it’s going to break down, end the set.
This exercise is challenging and will certainly be beneficial even without weights. If you can execute perfect form with your body weight, you can make the exercise harder by adding weights to your hands, by stepping on an unstable surface with your front foot (balance disc, foam pad), or you can place your rear leg on an unstable surface such as a physioball. You should be able to comfortably perform 2-3 sets of 10 reps on each leg before advancing this exercise.
If you tend to stand with a "swayback," developing awareness of the opening at the front of your hips is especially important. In Tadasana (Mountain Pose), practice lifting the ASISes, moving the tailbone down, and lifting the lumbar spine. Putting a belt around your waist, as you did in Warrior I, may help you increase your awareness of your pelvic alignment in this pose too.
Weight training aims to build muscle by prompting two different types of hypertrophy: sarcoplasmic and myofibrillar. Sarcoplasmic hypertrophy leads to larger muscles and so is favored by bodybuilders more than myofibrillar hypertrophy, which builds athletic strength. Sarcoplasmic hypertrophy is triggered by increasing repetitions, whereas myofibrillar hypertrophy is triggered by lifting heavier weight. In either case, there is an increase in both size and strength of the muscles (compared to what happens if that same individual does not lift weights at all), however, the emphasis is different.
Beach muscles and Olympic lifts draw more attention. But the many little stabilizer muscles around your shoulders, hips, and midsection — collectively the core — provide a strong foundation. Challenging the stability and mobility of these key muscles with medicine balls, physioballs, mini-bands, and rotational movements (lifting, chopping) pays huge dividends.