A lot of it came from self control. While a lot of it has to do with the fact that I played for quite a while (since the 1st month of release), I don't pull on banners unless I absolutely need to. Of the things I saw as needs:
Trinity
1. Wall (Sentinel Grimoire or Thyrus).
2. AoE Heal (non-shared S
3. Hastega
Everything else I've acquired was a consolation prize. Once I've had the trinity, everything else pull as I saw needed. If I lacked synergy for a particular realm, I'd pull on that banner maybe once or twice. However, now that I have multiple variations of the Trinity (I have both SG and Thyrus), tons of AoE heals (Yuna, Selphie, Vanille, a bunch of shared AoE Heals), and multiple Hastega relics (RedXIII, Sahz, Quistis) and a ton of synergy for the realms that matter (FF4 to FF13), I can just hold off on pulling randomly and just aim for the stuff I want.
From there, I just research ahead of time on what banners are coming out. Japan is typically 6 months ahead of us and knowing what's coming allows me to plan ahead for major relics like Ramza's Sword and Agrias' Shield. Seeing as how the FFT banner is good in general (5 amazing relics spread across 2 S-Tier characters), it'd be a good decision to hoard for it. I might not even pull on the SSSB banners coming up since I don't need them.
DPS relics, in my opinion, should never be chased because Power Creep is a thing in FFRK and it comes through the form of damage-based Soul Breaks. Unlike the Trinity, DPS relics do not hold well against the test of time. I've been using the same two Wall relics as Roaming Warriors since forever until I got my own. I've been using all of the AoE heals to a considerable degree. Sahz and Nanaki took turns on being in my party despite using the same aged relics. However, I've been sifting out DPS relic users from Rinoa to Squall to Cloud because I've been getting their DPS relics on the side of chasing the Trinity.