It doesn’t go in so far that I lie about my achievements but still, this concerns me. Should it?
Only if that boastfulness is meant to make you look better at someone else’s expense, or to make someone else look worse, or is done out of a need for praise from others.
The hard thing is interpreting others’ reactions to you. One person might be pleased and inspired by your success, and another may be a self-pitying curmudgeon who thinks you’re trying to make him look or feel bad. The former is what I’d call a friend ; the latter would be someone I rarely speak to unless necessary.
Ultimately, though, the line is one you draw yourself. Check your motivations, especially if you’ve habitually or unconsciously sought praise in the past. If you’re honest and conscientious and you’ve accomplished something, be proud of it, and don’t be afraid to let those who care about you know - and celebrate their accomplishments with them.
If you need some inspiration or an example, read Ayn Rand’s essay on Marilyn Monroe, Through Your Most Grievous Fault. An excerpt:
A woman, the only one, who was able to project the glowingly innocent sexuality of a being from some planet uncorrupted by guilt–who found herself regarded and ballyhooed as a vulgar symbol of obscenity–and who still had the courage to declare: “We are all born sexual creatures, thank God, but it’s a pity so many people despise and crush this natural gift.”
A happy child who was offering her achievement to the world, with the pride of an authentic greatness and of a kitten depositing a hunting trophy at your feet–who found herself answered by concerted efforts to negate, to degrade, to ridicule, to insult, to destroy her achievement–who was unable to conceive that it was her best she was punished for, not her worst–who could only sense, in helpless terror, that she was facing some unspeakable kind of evil.
Ayn Rand, 1962
While I’m not an actor or sex symbol (far from it!), I am truly inspired by a vision of flaunting natural, uncorrupted, self-made pride Rand saw in Monroe.