The search for truth must be undertaken with humility, and not used as an intellectual exercise to stroke our ego.
We all must decide what we believe and what we stand for, but it is very easy for that exercise to descend into self-exaltation, and for it simply to be an intellectual exercise to stroke our ego. If we're not careful, our attitude can become that "we believe only what can be 'proven', explained and therefore 'controlled', owned, or possessed by 'my all knowing mind/self'. This exalts me as master of the universe, knowing things by my own authority, with no need to submit to any Other." This attitude is closed-minded, already set-in-your-ways, and not open to learning. Similarly, when we talk to other people with differing opinions about truth and purpose in life, for that conversation to be an opportunity to flex our mind muscles and exert our dominance over "weaker minds". If you seek to convince someone else, you must guard against this sort of attitude in your own heart and seek not to win the day, but to win the man. References:  Gary Gray.