100% learned about tax saving from credit card research. Was looking into which cards give tax benefits, fell into rabbit hole of 80C/80D/80G. Filed better ITR last year.

The understanding compound interest thing (the hard way) - I missed ONE payment due date early in my card journey. ₹2,400 interest on ₹18,000. Never again. Now I understand why 'minimum payment' is a trap.

Expense tracking became genuinely second nature. Started because I needed category spends for card optimization. Now I budget properly, have emergency fund, invest regularly. Cards were gateway drug to financial literacy.

I started investing BECAUSE of reward point surplus. Had ₹15k in cashback/rewards annually, thought 'if I'm gaming the card system, why not learn investing'. Now have ₹8L investment portfolio. Cards → general financial awareness.

The fine print reading skill is VALUABLE. I review every contract now - phone plans, rental agreements, employment offers. Found errors/unfavorable terms multiple times. People think I'm paranoid, I think I'm thorough.

Credit score discipline transferred to other financial areas for me. If I'm careful about utilization ratio, payment dates, etc. for cards... I'm equally careful with EMIs, loan payments, investments. Cascading discipline.

Opportunity cost thinking is the real winner. I calculated: if I save ₹5k/month via card optimization + invest it at 12% returns = ₹10.3L in 10 years. That mindset now applies to EVERY expense. 'Is this worth ₹X of my future wealth?'

Counter-perspective: This hobby also made me MORE likely to spend in some ways. 'Oh there's an offer' = unnecessary purchase. I've bought things just to hit milestones. It's a double-edged sword.

@double-edged - Fair point. I've bought ₹500 of stuff I didn't need to reach ₹5,000 offer threshold. But awareness of this tendency helps. I track 'milestone waste' as a category now.

The subscription audit thing is HUGE. I was paying for 11 subscriptions, using 4 regularly. Card categorization made me realize this. Saved ₹4,800/year just from canceling unused subscriptions.

Interest rate understanding transferred to loan shopping for me. Got car loan recently, negotiated from 9.5% to 8.7% because I understood rate calculations. Dealer tried to confuse with 'processing fee vs lower rate' trickery. Didn't work.

This hobby taught me that small optimizations compound into big savings. 1% here, 2% there = ₹50k annually. Applied same thinking to electricity usage, phone plans, insurance premiums. Found another ₹25k in annual savings across life.

The tax benefit angle is underrated. I learned about HRA exemption, LTA benefits, 80G donations, all while researching cards with tax benefits. Filed way better ITR, got ₹28k higher refund than previous year.

Long-term thinking: Calculated that Infinia annual fee (₹12,500) amortized over 5 years at 3.3% reward rate needs ₹75k annual spend to break even. This calculation framework now applies to gym (₹15k/year ÷ 48 visits = ₹312/visit, worth it?), courses, everything.

This hobby indirectly taught me about investment vehicles. Comparing reward redemption options (cashback vs points vs miles) is conceptually similar to comparing mutual funds vs stocks vs FDs. Risk/return/liquidity tradeoffs.

Credit discipline is real. I pay FULL statement balance every month, BEFORE due date. This mentality transferred: pay rent early, clear loans fast, no EMIs unless 0% interest. My financial health improved massively.