Ah liquidity you wonderful monetary friend in case of emergency!
Funds that you put into your retirement account: roth IRA (post-tax money) or 401k (pre-tax money) should always be a percentage of income that you can afford to never touch. While I always put aside 10-20% of my money towards investments, I usually cap off the % of money for my retirment account at 5-10%. Also I keep in mind that there is an annual maximum contribution (varies by IRA type and your age).
I like having liquidity in my emergency living fund and my agressive growth investments just as much as investing for when I retire. Also, I really like self directed IRAs since I can mirror my personal investing style.
You should find a balance that works for your cashflow level, risk type and age. The Time-Value of Money really helps compound interest the earlier you start. This article is a great ground level introduction to what we our options are today for our retirement.